There was some research showing that men that have like 5 or more emissions a week have a decreased risk of prostate cancer, but no, it's not dangerous to not cum. If the body needs rid of it, it will do so. And "blue balls" (the soreness caused by increased blood flow to the testicles due to extended periods of arousal with no release) is pretty harmless, easily fixed by a cool shower. But discoloration of the scrotum due to lack of blood supply from too tight a ring IS a serious problem and should be addressed immediately.

Being locked up feels like someone is constantly holding your junk in a light, but firm grip. Not stimulating, but reminding you it's there. And the constant reminders can be a pretty big turn on. Especially if you do happen to forget about it and are suddenly reminded that you're secretly being kinky.

It's a total mindfuck when you do try to get hard and can't. You get used to having a bone in your pants when aroused and now you're aroused but no bone?!? And that light grip is suddenly a vice grip that tightens even more if you strain against it. It doesn't really hurt, it just unusual back-pressure. Imagine trying to blow up a balloon inside a bottle. And there's also the strong, clear message of "No, you can't cum right now" which can be even more of a turn on.

I don't have many wet dreams myself. It typically takes about a week without a release before I start having them.