How long does it take to charge an e-bike battery

They mainly use 18650 cells. So it would be reasonable to assume that a full charge and discharge cycle would be about 500 times. If you used it every day (really every day) from full charge to empty, that's only a year and a half.

But of course many things can help extend this. It would not be used every day, but on weekends and holidays. Also, you wouldn't drain the battery to 0% every day.

The best policy is to charge the battery so that the state of charge stays between 80% and 20%, which extends its life six times longer than using only the middle 60% of battery capacity. Since cooler temperatures increase battery life, do not store e-bike batteries in a water heater cupboard, but in a cold place such as a garage or storage shed.

Also remember that the running cost of an e-bike, even if you have to buy a new battery every year, is a fraction of the running cost of a fossil fuel vehicle, even a 50cc scooter.