I am going to tow my 2007 CRV behind my RV. The instructions in my manual say to only travel fo 8 hours at a time. My questionis, how long do I have to wait to begin towing again?

I imagine you would have to wait until the drive train/wheels/etc "cool off". So probably a good hour or so, assuming it's not incredibly hot wherever you are.

When you turn on key the gage for the Colling system doesn't move,or coll to the touch.don't do this and you may eat up the trans.

Use a tow dolly.

The CRV manuals for the 2011 (we used to tow one) and the 2014 (we tow one now), say all you need to do to tow longer than 8 hours is repeat the preperation steps you went through at the start of towing at least every 8 hours. We have done this many times with no problems or damage to the transmission. We usually repeat at around 7 hours just in case there is no convenient place to park for a few minutes at 8 hours. Read the instructions in the manual carefully. They're simple, but must be followed exactly.