I dont know how many is too many but I do use them all in regular rotation depending on mood or capabilities. Here we go:

FG, EM, FE x 2, FM, FM2n, FE2, FA, F2, F3, F4, F5, N90s x 2, N80 x 2, F100, N8008s, D5100, D7000, D600, L35AF

That's 22 by my count. Hey, is my wife going to see this??