I have 2,500 miles of mostly mountain roads on mine. Not squared off and look like they have a fair amount of life left. I think at about 3,000 miles I will switch to something better. They are not great tires, but they have served me well as I have gotten to know the bike.
I've changed the stock Maxxis after appr. 4K km's (2500 mi). Not because they were finished, but because they're squared off.
I've tried Bridgestone S22's and was happy about handling. Managed to get 5500 km (3500 mi) out of the rear tire. The front lasted a little longer, so I will replace the rear. For my upcoming holiday to France I decided to go for a fresh set of Metzeler Sportec M7's. Let's see how they will hold!
The way I ride, it's going to be a long time before I need to replace the stock tires. Someone here said that the stock tires are perfectly fine for the street so I'm going to hold out for as long as I can.