Razer Laptop Power MOSFET replacement
A Google search reveals that they fail because they overheat. The Rds is very low, so that is unlikely to be the problem (assuming that it is fully turned on). It could be that the Vgs is too low and it isn't fully turning on. Or, it is used in a PWM circuit and it is switching too slowly. You would need to scope a working circuit to diagnose the marginal design issue. 

I would not recommend attempting to substitute a different part without a diagnosis, you could make it worse. 

You might consider attempting to heatsink it better, but space is tight in laptops and it is unlikely to have enough space. You could also block airflow and make it worse.