Wheelchair and scooter batteries come in a variety of qualities. They are rated in cycles ( How often you can discharge them then recharge them and have them still work ) as opposed to over how many months. The warranty may say something like they are one year but technically speaking, you want to know how many cycles you will get from them for the money.
The batteries designated EV (for Electric Vehicle) will outlast any generic battery for any purpose of any size. For not much more money, you will get a lot more battery. Taking care of these batteries is critical to their long term health.
Start by charging the batteries after every use of your wheelchair. Run them down, charge them up. Even if you only used it a little. Batteries like to be in use, so this keeps the chemistry active. In fact batteries don't even reach their full range until they have been discharged and recharged (cycled) a number of times.
We recommend you unplug your charger once your batteries are fully charged up. While the chargers are supposed to be able to stay plugged in once charged, we find too often the charger keeps charging and can swell up and ruin the batteries.
So. Use the wheelchair. Charge the wheelchair. Unplug the charger once charged. If it is going to sit for more than a couple weeks, plug the charger back in. DON"T let the batteries just sit, unused.