I can give you a fairly definitive answer based on the experience i gained working on electric vehicles.
Full traction batteries are capable of being charged with very high currents,
and of being cycled many times, unlike SLA (starting lighting and auxiliary batteries). they are more robust mechanically and electrically than SLA and leisure batteries. which TBH aren't much beter than a heavy duty SLA especially the cheap ones.
However any battery left in a discharged or partially discharged state will start to sulphate, which will ruin the battery and is a largley irreversible process, the way around this is to keep them charged all the time, and recharge immediately after discharge.
so to sum it up any lead acid battery left in a state of partial charge is buggering up as time ticks by.
regular charging or more capacity to lessen the depth of discharge will help;
I am usually not as green as i am cabbage looking.