I am not a heavy user anyway but bought it used from Ebay from a trusted game store with firmware 3.41 on it and one of the first things I did was take it apart though it looked brand new inside and clean the internals and put upgraded paste on.
Since I have got it I have only used it about 12 times in 8 months but I noticed a few times I went to turn it on and just got a black screen, everything worked like controller synced and the blu ray drive ejected and read just no picture, and when this happened just left it switched off for like a hour(more I think) then it magically worked.
Once or twice it didnt work but again just left it off for about 2 hours and it suddenly worked.
I then got GTAV on release and played it most days for a week for hours a day then didnt play it for 2 weeks a few missions before the end and when I went to turn it on same problem.
I left it off a hour or so a time and nothing so left it off overnight and it worked first time when I tried it in the morning and the couple of times I have turned it on to test since and doesnt show artifacts or anything and the fans are normal speed.