I got up to 885 hours one time. The higher it got, the more I started aiming for 1000. I finally had to reboot due to a few glitches that started happening (the main one that made me reboot was that the music player kept randomly stopping).
Just to update, it does roll over into 4 digits. Feels like the Seinfeld episode where they ride the car from the dealership down to the brink of E on the gas tank.