Normally CPU can last above 10 years. MB can fire earlier than that. 7 years is like you pulled all, thats great.
A person can run a CPU without heat paste at least of testing without much problem. If it over heats then the system will automatically shutdown.
I am a certified for computer hardware. Forget about paste, I had once run a Pentium 4 without heat sink at 102°c and it was ok. It was for a short duration of time.