sleeping nude is great if you want to relieve some stress. You get used to the frequent boners. I have to say, I usually sleep nude, but when it is extremely cold, I usually wear a t shirt (JUST a t shirt) or just some boxer briefs. You body gets used to the cold quickly
A lot of my friends sleep nude, I know, caused I've seen their boners while sleeping!
I also freeball sometimes, most of time in the summer.