If you only have one costume, I do suggest changing into civilian clothes at some point each day to let your costume air out (you can use this time to shower!
) and people won't really give you a hard time for not cosplaying.
I try and get a costume to wear each day, and at least one new costume each year. I tend to have all sorts of crazy ideas for costumes that don't really come together so I use back up ideas. My Hermes the motorad costume is doomed unless my dad comes through with some parts, but I'll still have a couple of new costumes to play with.
The only day where I'll run back to the room and change into a new costume is the day of the cosplay contest, in case I need a costume for the show that I can't really wear all over the place or I want it to be a surprise. In fact, Comic-con in San Diego makes people competing in the costume contest NOT wear their costumes before the contest. It can get you disqualified!
Basically, bring as many costumes as you can and change if you want to get a photo with someone or you're taking part in an event. It's no big deal.