You can wear them for up to a month without taking them out.
I live outdoors/camping for a month setting up for our festival (so most of July and into August), and then went to BM last year. Used one pair from July - Aug, put in a fresh pair for Shambhala, then put in a fresh pair for BM at the end of August. Always kept eyedrops handy, but rarely needed them. Definitely one of the best decisions I made for that summer, comfort wise.
I went back to my regular contacts for this summer. Even though I didn't do the Burn this year, after having it so easy last summer, I found it was a real bitch to take them out every night while I was on site for our event.
Will def. be buying them again next year, and using them during future summers even when I don't go to Burning Man.
"the aim of life is to live, and to live means to be aware - joyously, drunkenly, serenely, divinely aware." - henry miller