It is ! This extra information about there usage may throw a bit more light on your issue. It would appear they are well used. Out of interest, how much solar power do you have and can you tell me what leisure batteries you have. (Did I read earlier on that you had 2 Banner lead acid batteries ? if so, that will 200 cycles at 50% D.O.D). If you have been doing a shed load of days out and not using Hook Up, the amount of Solar Power (S.P.) you have is going to be important and the amount of good daylight they will be exposed too ? Assuming you have more power coming from your panels than your using during in daylight hours then your leisure batteries will not be loosing any power and more importantly not cycling. At night, they will be using power and therefore cycling. The amount of Cycling will depend on how far they are discharged. (if you discharge by 50% and then fully charge again, this is one cycle. After 200 cycles they die no matter how much charge you put into them after that point). The drop test referred to above by Pausim will help you establish how healthy your Batteries are. Unfortunately, it wont tell you how much life is left in them as you can still fully charge a leisure battery that has very little capacity left.
they are Bosch battery’s and I think they are the ones you stated. I bought Bosch thinking they would be the best,I didn’t realise the cycles they do. I also have a 150w solar panel,and as most of are days out are always in daylight the batteries wont loose much.