I have one that has seen daily use of average 8+ hours a day since it was $600 (Not Launch but before the first revisions)
The key to longevity is externally cooling units. I really love the one Pelican made but after about 7 years of service it died. I couldn't find a replacement but if you can I recommend that one. Gets a little loud when it gets old but its worth it since its temperature controlled so it will keep going after your PS3 is off if its still hot.
When my Pelican died I replaced it with 2 units. A front and back fan. There quiter than the old Pelican, not a new one, but, they use the system for power so they turn off when the system turn off and are sort of ugly. Though they seem to be getting the job done.
I would recommend one of the first things you do is replace the Harddrive as well. I need to on mine, still have the 60gig, but, the process is more of a pain than a benefit for me at the moment with having to backup and redo everything.