I'm running 31x10.5 TSL's and have yet to wear them out. I've had mine a little over 2 years. They do flat spot as well, but I keep mine at 10psi all the time, on road or off. I'm sure if you ran them at a higher pressure for the road, they wouldn't flat spot as badly.
I have known three different samurai's to run the thornbirds (we call them super chickens), and none of their owners liked them. However, the two guys I know that have big trucks (full-size chev's) swear by them. If your going to run them on a full size rig with plenty of H.P. to spin the tires, they seem to work OK, but a samurai is just too light and underpowered to make them work.