>>3480
Well in general my opinion on Watts and that whole school is that it's a cult. Keep an eye open and you just might notice what I'm talking about.
Now sure, you can get a little rusty but it's not like what you've learned somehow disappears. It takes a while to get into the swing of things if you haven't done it in a while but that's the way with everything. Another thing to note is that you're often still using skills that aren't obvious in the work you do. If you're doing a still life painting, you will still be thinking about proportions, gestures edges and so on, even if you're including additional things to consider like color.
Just some personal things about this is like if I haven't done a quick-ish (3 hours) figure drawing for a few weeks and I've been working non-stop on my cast drawing or something, just picking at details all day. My figure drawing tends to come out fairly well because I feel free to just push other aspects of drawing that I haven't had a chance to work on for a while. I've sort of returned with a fresh perspective and now with more knowledge that I've accumulated elsewhere, I can tackle a quick drawing with a new and strong approach.
So for me, the argument that you might benefit from switching subjects can be valid but not because you loose in the areas you aren't working on but rather you stagnate in the thing you've been doing and you need to do other things where you can solve problems in a different light, that you might not otherwise have been able to solve in the current thing you were working on. I tend to feel as if when you sort of get comfortable with a subject and start to feel like "yeah I've got this", you switch because that comfort means there aren't glaring challenges starring you in the face and it is that kind of challenge you need to efficiently learn.
Now it's really difficult to know when to move on and how long to study a certain subject but don't be afraid if just getting into something for several weeks. If you're on a roll and you're learning one thing after another, why stop if it's working? That momentum you have should be used.
There is however value in sticking with something when you're up against a wall. Notice how I mentioned that you can change subjects when you're comfortable with a thing, but when you hit a point where you're like "I have no idea what to do", that is an excellent opportunity to really push yourself one, two or ten steps further than you would have thought you could go. I never would have thought I could spend 10 weeks on a cast drawing but I have done it and it was really valuable for me to do so. Getting to that stage in a drawing 5 weeks in where it looks finished and having to ask yourself "what now?" is a place where you really are starring into the abyss and being able to overcome it is (I believe) what will often separate the good artists form the great artists.
So, If I may suggest a schedule I believe to be very effective, simple and stress free. It goes like this for every day of the week (or maybe except weekends), Project 1 for 3 hours, project 2 for 3 hours and then an extra, alternating project for 2 hours. This extra project can be whatever you want, consider supplementary study time if there's something off topic you're interested in. You can change what projects you're working on every week, every other week or when you feel like you can point to something and say "yeah, I learn that thing". When you switch all the time, it is hard to know if you're actually learning anything at all with can lead you to be inefficient without knowing it.