I think this brings up a couple of points which are worthy of discussion. Your post seems to echo a sentiment that I have come across before, which is the belief that Mentor and Instructor ratings are part of the natural progression of a controller's career. I have been approached by controllers in the past who seem to think that once you have obtained your C1 rating, you should immediately proceed to become a mentor and instructor in the same way that obtaining your S2 means it's time to start working on S3. In my opinion this is quite far from the truth. Perhaps the scalar nature of controller ratings on VATSIM has led to this belief, the I1 is above the C1 and thus is higher up the ladder and must be more important.
It is interesting that you refer to an Instructor position as a "promotion", in the sense of being passed up for promotion. Perhaps I am unique, but I do not see a Mentor or Instructor position as a promotion at all. Instead, I think of a training position as an additional task. That is to say, instruction is a duty one undertakes in addition to whatever other roles they may have. Much in the same way that ARTCC staff have duties which they have undertaken in addition to their roles as controllers, I think that instructors are merely controllers who have volunteered for the additional work of training new members.
I think when we are students, we learn to look up to Instructors and Mentors as people of higher rank than ourselves, and perhaps rightfully so. After all, these are the people who not only passed on their knowledge and experience, but also determined when we were ready to control online and ready to take our exams and OTS's (and hold our fate in their hands while deciding the outcome of an OTS ). I think perhaps that it is easy to still think of Instructors as being of a higher "rank" when one becomes a C1. I don't really see it this way though. In terms of controlling ability, I think of an Instructor as being generally the same as a C1. In fact, some of the best controllers I have known on VATSIM have never been (and have no desire to be) involved with training.
I think the things that make a person a good instructor are different from those which make them a good controller. The tasks associated with controlling and instructing are very different, and in order to be an effective instructor it is necessary to master both. Obviously in the course of obtaining a C1, we learn the skills necessary to be an effective controller; however this does not teach us how to be effective instructors. An S2 trainee learns how to sequence VFR aircraft in the traffic pattern, but the task of the instructor is to effectively convey this knowledge and experience to the student, and to make the *student* good at sequencing aircraft. It can sometimes be difficult to teach a student to "see" a situation in the same way we do, and to effectively utilize the tools at their disposal to handle a situation effectively.
In addition to this, instructors must be more than mere faucets of information from which students may drink or drown. Rather, they must often provide *motivation* as well. In my (still ongoing) time as an instructor, I see my role as not only teaching students how to control in the way I do, but also to teach them to enjoy controlling the way I do. More than once in my career as an instructor I have seen students who are literally ready to give up on controlling having faced a number of instructors who simply spew information and expect the student to grasp bits of knowledge as they fly by. Even worse, there are many who merely wish to hold the rank of MTR or INS as a badge of seniority and have no interest whatsoever in the success or failure of those they teach. My point is not to rant about ineffective instructors, that will always be an unfortunately reality in an environment that operates on the scale that VATSIM does. My point is that when faced with these students, my task was *not* one of teaching them to control at all. My task was to teach them to enjoy controlling again first, and only then could I worry about passing on skills and knowledge.
Overall, it is not enough to be a good controller. Nor is it enough to be a good teacher. You must be a good controller, *and* a good teacher, *and* a good motivator. Perhaps it is counter-intuitive, but the mark of a good instructor is not the skills and abilities they posses. Rather, the sign of a good instructor is in the skills and abilities of their students. So for anyone who has spent some time as a mentor and thinks they are ready to become an instructor, my question to you is this: Who are your students? How many of them have become C1s? How many of them are even still around? When I think about my (reasonably successful, though certainly not stunning) career as an I1 I don't point to what I can do, or what I have done. I point to what those I have taught can do, and what they have done.
I would also like to take the opportunity to address the idea of transferring to another ARTCC in order to become an instructor. I expect many people will point out (rightfully so) that it takes a significant amount of time to gain the necessary familiarity with the airspace and procedures of different facilities before you can effectively teach that information to students. As such, I won't discuss that in detail other than to say that this is very much true. What is also important (and sometimes overlooked), is familiarity with the culture and the student body of the ARTCC in which you teach.
I don't think anyone would argue that the ARTCCs of VATUSA have very unique cultures. While we all follow the same procedures, there are many areas in which we control and operate differently. I don't expect that flying in ZHU or ZJX is going to be the same as flying in ZNY or ZLA. If nothing else, the difference in density and traffic volume alone make for a very different experience, both as a pilot and as a controller. One of the side effects of this is that the ARTCCs *do* have their own unique cultures. Personally I think this is a good thing. I enjoy flying in many different areas and getting a different local flavor depending on where I am. As an instructor, it is not enough to know the policies and procedures at a high level (as in "how to vector airplanes"), nor is it enough to know the policies and procedures of a particular facility. You must also be familiar with the culture of the environment in which you are teaching, and I think this can take longer than learning the airspace.
While it is impossible to put any kind of exact number on this (I would *never* say "You must be a member of an ARTCC for <X> days/months/years before you should be an I1), I can absolutely guarantee without hesitation that I would never consider making someone a member of my training staff until they are extremely familiar with not only the airspace, but also the culture and the students of the ARTCC. Anything else would be a formula for disaster.
Please be aware that *none* of this is directed at you personally. I don't know you, and I don't know your abilities and experience. You may well be the best teacher in VATUSA. I simply wanted to address the perception of instructors and mentors as senior ratings to which one is promoted, which seems to be quite common.