With a proper charge controller - the on board converter/charger if on shore power - or the solar charge controller - neither should damage or shorten the life of the batteries.
One could argue the quality of a solar charge controller you might buy compared to the quality of the Thor provided converter/charger... but if concerned - you could always replace the Thor provided unit with a better one... I haven't done so - and have had no issues.
Proper battery maintenance (checking water levels) should tell you if you have a problem... I wouldn't expect to have to regularly add water to a healthy battery being properly charged/maintained.
Not yet retired...
Florida (Michigan transplant)
2014 Hurricane 32A
2000 Infinity (previous)