I used to run mine at 20 front, 25psi rear, but a bit more pressure and they will last longer - they are a pretty soft compound, the old traction/wear thing. Problem with the K70 is the rain groove and half the cross grooves aren't full depth, so at half worn they are nearly gone, and so has the gravel traction. Actually you can control traction with the throttle, where it goes pear shape is engine braking - chop down a gear on corner entry and all traction is gone.
I have no idea how long mine lasted - well, 4 years, but I have 2 sets of wheels, so mileage is unknown. But by this stage they were not a lot of fun.