From what I remember from Beagle, the sprockets will start to see accelerated wear when the pitch of the chain deviates from the pitch of the sprockets. This occurs when the chain elongated due to wear. The result is that all the torque load is concentrated in the first two or three sprocket teeth causing the teeth to wear at a much higher rate. The remaining teeth are unloaded and are simply accommodating the chain for the ride in a semicircle.

So, with a chain that has not worn excessively, the sprockets will probably last forever.