I often get called out to look at Batteries, people sometimes buy the cheap ones online, please avoid these! They are cheap for a reason, whilst the feedback is generally good that is because people submit feedback shortly after purchase, not later on. I have replaced so many cheap batteries that only last a year. I have also tested brand new cheap batteries that are only half the capacity advertised. How long batteries last WILL depend on how you look after them and being sold the right ones in the first place.
We then get into should you have AGM or Gel batteries. It will depend on what your use is, for someone that uses a scooter or chair daily for long periods then GEL are the best option. For those who use it occasionally then AGM are perfect.
PLEASE NOTE: This is just a brief breakdown of batteries, should you need new batteries I will discuss with you all of the options and work out what is best for you, not what is best for me! When I worked for a large mobility company their policy was fit GEL to everything, not because they are the best for every customer, it was because they made more profit on them.