It’s really up to you.  Some people have a costume for each day, some people have one costume they wear all weekend, some people do variations of the same costume (so like, maybe a rave version for the rave, or a pool version if they want to go swimming, ect.), it really depends on you.  Heck, some people have multiple costumes throughout the day, like, Friday morning, Friday night, and things like that. There really is no set standard.  

I used to wear one costume for the whole weekend, but as I cosplayed more I got more cosplays to do throughout the weekend.  It really doesn’t matter as long as you’re having fun with it  :)