How long will my computer's performance last if i leave it on 24/7?

I recently bought a HP Elite 8GB Ram, 2.8GHz 6 Core AMD Phenom II. I bought it for gaming. so i keep it running 24/7 and maybe shut it off once a week for a couple of hours. I want to know how long will it take until the performance starts to "suck". Thanks in advance. Tips and answers are appreciated.