Alot of times freezing happens right before the consoles YLOD's (term used for hardware failure - mostly caused by internal CPU/GPU problems on the console).
2 years is about the same time mine failed. (Bought it in 2008, failed late 2010-early 2011). If it YLODs, only "permanent" solution is to send it in to Sony and pay $150 to get it "repaired". However, if they send you another "phat" model, it's a chance it'll YLOD in another 2-4 years. May be worth to just buy a new slim model (what I did) and avoid Sony CS.
I put quotes on permanent because there is a way to "fix" YLOD, but it carries huge risks including the console exploding or catching on fire... I wouldn't recommend trying it and for safety reason, I'm not going to mention how you can do it.
Edited by NpaMA, 28 August 2011 - 05:36 AM.