This really depends on how often you use the mobility scooter. If you use the mobility scooter frequently then you may need to replace the batteries sooner that someone who uses their mobility scooter only now and again.

It is extremely important to look after the batteries, by keeping them charged and not letting them get fully run down to empty.

If you notice that you cannot travel as far as you used to on your mobility scooter this could be an early indication that the batteries need to be replaced.