Yes, this is true. I wash the towels once a week to be sure. I choose to use towels because I get paranoid about having standing water other than the water dish in the enclosures. Mainly because I do not want the snakes to rest on anything that is damp or wet.
Also, I agree with you about the rheostat.
This brings up a question I would love to find an answer to. If you are trying to maintain temperatures in three different 'zones' (i.e. warm hide 90, cool hide 80, ambient temp 80) in a display type enclosure, do you need three different thermostats? Is there a super thermostat out there that has multiple probes attached to multiple outlets?
Jimmy