If your doing menial tasks (Such as replying to emails, writing letters, browsing the web) your CPU shouldnt go above roughly 60, however if your putting stress on your CPU (Such as gaming, modelling) your CPU should still stay at a stable <90. If it does go above 90, I suggest getting a better cooling system, and if its going high enough to shut down then I would look in to a water cooler or an additional fan.