I'm looking for something similar to what I've got in front of me right now. It's not a research trial, but it's written by a vet (the book "What's wrong with my snake?" by Dr. John Rossi).

He says the preferred duration is for a 1x1" strip to be used for 3 hours every 3 days for 8 weeks (water removed during the time that the strip is actually in the cage). He links over-exposure to paralysis in garter snakes, severe neurological problems in pythons, and lethargy in water snakes.

By the way, here is the type of setup in this zoo I'm referring to. You can't tell in this photo at this resolution, but that water dish is empty.