I sometimes use warm water to soak gear so the salt crystals will desolve faster, and then I do my final rinses with cool water. I believe hot water could cause some breakdown/weakening of some seams, fabrics, rubber parts, silicone parts, seals, etc., especially with regulators over a period of time, so I stay away from hot water rinses and soakings.
I do most of my rinsing outside, except for soaking my regs, because it's quicker and easier for me to spray things off outside than having to clean up the bathroom. After week-long dive vacation trips and before storing gear for the winter, I give everything a nice long warm water soaking and cool water rinsing in the bathtub.