I have yet to do more than three cosplays for a con, or more than a single change in a day. Admittedly, part of this is that I've got a lot of sewing to do to finish up things that are
almost there -- once I'm past that, Toomuchtowearcon, here I come! Part of it's also transport: I'm flying up for Kcon, and with airline restrictions on baggage, the less I bring the better. (That said, I've planned for three and just maybe a fourth if I'm insane, and I'm already posting things up to my family to bring down because I can't bring them on the plane.) Part of it's just laziness.
![Cheesy :D](https://www.kumoricon.org/forums/Smileys/default/cheesy.gif)
My baby sister tends to change two or even three times a day, most days. I'm not sure how many she's got planned for Kcon, only that there are a LOT. It never seems to bother her to do that.
I think, if the hotel's close enough (unlike AX this year, for example), that doing more than a single cosplay per day's not a problem, unless perhaps there are extensive makeup details or stuff like that. Some cosplays you don't want to try to put on in a rush, and a lot of the time, changing seems to come with that. It also depends on what con is for you, I think -- if it's about cosplay, then that's different from those who go for panels or gaming or whatever.
... and I have no idea if this answers any of what you were asking.