YOu're definitely overheating if it takes longer to shut down the longer its off. Try putting a fam right next to the computer, see if it takes longer to shut down. If it does, then you need more fans in your case. Don't go for liquid cooling unless you have like, four video cards, it costs about 700 bucks.
Got a mini fan and it blows on the back of the computer and it has not gone off the whole day, thanks everyone(especially Condor)