Depends on what day of the week it is.
I've probably had my best hobby experiences with women in their late 20's/early 30's, so I picked 30's. However I've also had plenty of mind-blowing times with women in their 40's and 50's (Aphrodite comes to mind, what a woman!). For me it depends more on attitude than age. Usually I avoid the younger ones as they're less likely to have their shit together (in my experience). However, even then there are exceptions--most recently Melanie V, less recently Plaything (Toi, ah such good memories).