[DonRotolo]

It is a lot for FRC applications, considerably less if you want it to last a normal lifetime. I would think the limiting factor is the shaft bushing (and the resulting friction), since the shaft itself is fairly stiff (it should support several hundreds of pounds without bending). You can dramatically increase overall side load capacity by installing a roller or ball bearing somewhere along the shaft, even if it is between the gear and the motor case it can carry a lot of the load, or ideally at the far end of the shaft.