Should I get my ps3 replaced or keep it?

Well I notices that when I play black ops on my ps3 sometimes it doesn't load as it used to it takes like 5 seconds then it should and earlier when I tried to play zombies kino it didn't load it just staid on a black screen and I had to hold the power sensor on it to completely shut it down it happens twice so the thierd time I took out the game noticed a smudged no bigger then half an inch and wiped it with a cloth put the game back on and it worked fine and the kino map loaded right away.....another thing is that I don't take out my cod game out when I turn it off I just leave it there and turn it on with it in there does that ruin the system