To all those sleeping in your soft contacts, let me tell you from experience - Don't do it!
I ended up having to wear glasses for 2 months because my eyes got so swollen and I didn't even know it.
Then a few months down the road I started having trouble even only wearing the contacts for 4-8 hours a day... The swelling apparently never went away completely and changed the size of my eyes. I was wearing contacts that were way too small and ended up depriving my eyes of oxygen. Another 2 months of wearing glasses and 1 small white spot on my cornea, I'm finally wearing the right size contacts again. Luckily, the white spot is on the edge of the cornea and not in my line of vision.
Trust me, its not worth the trouble down the road. Just take your contacts out every night. You can sleep in them every now and then, but if you wear them constantly you're asking for trouble. I was very lucky not to have permanent vision trouble because of it.