My instructions were ten minutes and no food or drink for one-half hour. Rather than mess around, I just wear them for at least a half hour, sometimes much longer if I am reading or watching DVD.

What I don't like is the excess gel in my mouth -- I drilled a small (1/16") hole in the cap and now when I squeeze the tube only a small stream comes out in the trays, so there is less excess gel in my mouth.

I also use a tongue cleaner, plus rinsing, to get the excess out of my mouth. I happen to have both kinds pictured. The scrapers are also useful to clean out the junk that builds up from nutritional drinks like Nutrena, Ensure, VHC, etc.

http://en.wikipedia.org/wiki/Tongue_scraper