I have 9 right now, though only 3 of them are >$100. I'm definitely a bit of collector, but I make use of all of them regularly except for my MDR V150, which is now permanently retired. For example, I have one for work, one for my home listening station, one for my home desktop computer, one for the basement library, one for drumming, one for my keyboard, one for walking around the house, and one for the gym.
Edit: up to 10 now, with 4 >$100.
And I do a lot of switching as well. Depending on the song, I will sometimes swap headphones, amps, sources, or adjust EQ settings. I enjoy hearing a wide variety of presentations and sounds much more than one "perfect" setup that will supposedly work for everything.
Edited by LithoJazoSphere - 12/27/11 at 1:34pm