A good O-ring chain, like a DID, should last for the life of the motorcycle on an electric bike. I typically get around 35,000 miles on a DID 525 chain on a 4-cylinder motorcycle, like my Yamaha FZ1. Chains hate being hammered by something like a single-cylinder engine, but the more cylinders you have and the smoother your engine runs, the longer the chain will last. Being as no IC engine is as smooth running as an electric motor, I would expect a very long chain life on an electric motorcycle. But I will admit that I hate the task of oiling the chain and cleaning up the resulting mess all over the rear wheel and swing arm after a few miles on the road.