I just did my CCR cave course. Did it in a combination of wetsuits, most dives were in my 3 mil, some in a 5 mil, and almost 4 hours at Peacock in a very used rental 3/2 mil. That was a cold day.
I have a drysuit that I've never had in the water. For the most part I was good for several hours in a 3 mil, the 5 mil was obviously more comfortable. For cave diving, I think I should switch to a drysuit for the backup buoyancy. In a trilam suit, for 72 degree water, I'm thinking just fairly light base layer would be OK. I've found a few on Amazon that look pretty decent. I also have a Sharkskin Chillproof wetsuit that I think might be a decent option, unless I decide to go with the p-valve.
I have a pretty high tolerance for cold water (to a point) but would like to warm up a bit for better deco on those longer dives.
Thoughts?