is it irritating to hear stand-up comedians continuously laugh during their performance? I decide for myself if the material has any merit .?

It's worse when they PRETEND to laugh... like they've JUST realised it's funny.

Just because the comedian is saying it doesn't make him somehow immune to the humor, even if he's the one speaking. If you have never laughed at anything you were saying yourself, you may not see why/how it's funny, and be at a loss why other people are laughing.

That said, it can also be a deliberate leading behavior. If you want someone to laugh, laugh yourself. It's a fact that others will be more likely to laugh if you're laughing already.

You decide for yourself, but the comedian's goal is to make everyone laugh so he has a vested interest in presenting the most humorous material he can. That means he will find it funny himself - and be more likely to laugh at it even as he is presenting, and will be inclined to try to motivate you to do so as well.