Mine work nearly all the time for both the 757 (4.4) and 767 (1.4). Only once in about the last 15 or so flights have I had them switch off when the wheels touched the ground. And that was in the 757.

I try not to turn on the Autobrakes until I have slowed to about Vref +30 and my flaps are at my chosen landing configuration in the FMC. e.g. In the FMC I have chosen 20/140, I won't turn them on until my plane is flying at 20/170. This seems to work for me.

Mark