yes. i always figure that if you ask your students to do something - you should be able to do it, too. (with the exception of that piece you've always wanted to hear and never had time to play).
my most recent teacher has changed my 'philosophy' of exercise, though. he probably uses minimal exercises and more 'brain' exercises (what i mean is playing a lot of off beat things and getting your brain to 'click in' faster in terms of what the fingers do). it's usually repetitive but the accents are different every measure. maybe what you are saying, too, to do a variety of different exercises and not become stuck on one thing or other. repertoire does this. you have so many different challenges and difficulties - and you can take 5-6 to -10-20 measures and repeat with different techniques to achieve the result. i've learned from my teacher to not do things the same way over and over but to EXPERIMENT. i was not much of an experimenter with sound before i had him. sort of relied on 'gut instinct' and never would 'rework' the sounds or ideas - but blindly repeated them as i learned them.
it's sort of like acting. you take something and try even the most dramatic approach. and then, keep toning it down. so you see the one extreme, the middle, and the other extreme (and a few in between). so, when you come to a crescendo - you might wildly play it PAST the point of the crescendo peak, and then gradually pull it back.
five-finger exercises are my fav's - and, scales and stuff to stay 'in form' - but i never have time for that as much as repertoire now because of limited time. you never want to OVER practice. i'm realizing that now. protecting your fingers/hands is extrememly important. if you do a lot of technique, then go on to repertoire for a little while. but, whenever your hands are sore. stop. do something else and then return. probably the key to practicing longer and longer is to constantly remind yourself to relax and not to use ALL your energy. to reserve it (like a long distance runner). you don't have to play all exercises forte (or any,a ctually). muscles in the fingers, i've learned, is pretty much only helpful if you are playing thirds or certain trills. most things you have to deal with are on the 'brain level' of achieving the right fingering, the right sound, and the right approach (flat fingers for most things - results in a 'petting the sound' out of the piano).