I spent 39 years with the phone company. They have a lot of batteries out in equipment huts and have done lots of research. Batteries last the longest when maintained at 100% charge. A really good battery maintainer will add to the life. Avoiding very high and very low temperatures helps as does reducing vibration.
The only real improvement in sealed lead acid batteries is the glass mats, between the plates, in the AGM batteries. They improve the internal resistance and keep material that is shed from the plates from dropping to to bottom where it can create a short.
I won't buy any battery that isn't AGM.