It's not running beautifully, it's running awfully and you're going to damage it. No, it probably won't break in a week, but you do not want to risk it, I mean Intel says the max temp is 60c, you're fine up to 75, but 100 is just way too high. It's just dumb to reuse thermal paste, and it seriously is not difficult to reapply. I'd be happy to link you to a very thorough guide that makes it easy, or walk you through it myself. It takes me about three minutes to reapply thermal paste.