Before I started purging the collection, I had 10 or 11, I only used like 2 of them continuously, so I sold everything else, and have recently started selectively trying out new models. I do not want to go back to 10 or 11.
The list was:
AKG K701
Audio-Technica ATH-ESW9
Koss ESP/950, ESP/10, KPH7
Sony MDR-SA5000, MDR-F1, MDR-EX082
Denon AH-C751
Kenwood KH-K1000
Sennheiser HD 580
And then intermittently I had both Bose around-ear sets, both Ultrasone open models, and another pair of Koss cans on-hand (but have not had 15 at once).
And I called it: wire madness!
From that, only the ESPs, IEMs, and F1s remain. I feel weird selling the IEMs because I've used them (it seems unhygienic - not that I'm unhygienic, but I feel weird selling something like that, just like I'd feel weird selling a comb, pillow, or hat), and they need new tips anyways.