Fairmont High Beams Turn off in 5 minutes

Hi guys, I have a fairmont from the 80-90's im pretty sure. I am not sure of the exact year. Anyway Whe I turn my high beams on they stay on fine for about 5 minutes then they just turn off for no reason. Then with every succesive attempt to keep them on they turn off sooner and sooner. It has a small oil leak, but other than that it has had no problems that would relate to this problem.

Thanks guys.