Leisure batteries are not up to the job. You need to check out the deep cycle gel batteries, they are dearer but they will last longer.
I reckon the battery manufacturers are just about sussing out the kind of battery that we need, because the kind of demand we put on these batteries is quite unusual.
I have thought about the solar panels, as well as the split charge relay, to help keep the battery topped up, but haven't bothered since getting this new battery, it has a 10 year guarantee, so we will see.