I'd think it more possible to slide in cold weather personally, but you are doing something right if its not sliding.
As to sling comfort IMHO a stiff wider leather sling is more comfortable than one like the cotton one thats skinny and conforms to your hand more, because it can cut deeper and have more contact, the stiffer wider one seems, at least for me, to spread that tension out over a wider area for some reaons.
As to repetition, yes, but correct repetition must bue used. And you have to consider both relaxed AND NPA, at least I do, a number of times during even a slow fire string. And twice during a rapid.
As to snug vs tight, the only thing you need see, is the test I mentioned we use when coaching. IF the rifle is one with you, you are fine. If not, then it needs to be snugger.
