Heating the nut with a propane torch seems to be far more effective than PB Blaster. Although theres plenty of spots you can't get a torch to the nut, so PB Blaster may be your only alternative in some cases. Propane Plumbing torches are about $13 at your local hardware store.
I've treated bolts with a shot of PB Blaster everday for a week and they still snapped off. Last night, I couldn't loosen the Parking Brake Adjust Nut, it was siezed, and I had been treating it everyday for a week with PB Blaster. The adjusting bolt on this thing is special and it looked I'd have to replace the whole thing if I snapped it. So, after a reasonable attempt to break it free, to no avail, I removed the whole Parking Brake Tensioner, put a Propane torch to the nut got it glowing red around the edges, and the nut backed out like butter.
It was a nylon sleeve lock nut though, so the nylon insert burned out. But a nylon insert lock nut at the harware store is a lot cheaper than a whole Parking Brake from the dealer or a Junkyard.
I finished brakes last night, I'm about to get started drilling out all the other bolts I've broken. 3 out 4 rear shock bolts (treated with PB Blaster) and 2 out of 4 bump stop bolts (not treated with anything). I plan on changing swaybar bushings, I'm worried those bolts will snap as well. I've yet to repair the snapped exhaust studs, I got with the vehicle when I bought it a couple of weeks ago.