No personal experience, but I know I've read somewhere that you can maintain your current level, but not try to do any improvement - ie no speedwork or hard workouts, just maintain your current level, adn definitely don't start anything new. It makes sense to me, if your body is already used it. Know a woman who was a Spinning instructor - she taught up to 6 or 7 months! Just let herself slow down a little later, when she was bigger.