I have had two wet cells and now an AGM. The first battery was a wet cell (OEM came with truck new), lasted 7 years. My second battery was also a wet cell (Interstate, direct replacement of stock specs), it lasted 5 years. My last battery is a Napa Legend AGM. I noticed that it seemed to be getting marginal charge wise after only a few years. I had just replaced my alternator, for a whining bearing, otherwise it seemed to charge fine. I assumed the alternator was not working as it should and that was why my expensive AGM seemed on the way out.
I did some fooling around and with the help of a few senior members here found I just wasn't getting a full charge on my frequent shorter trips. I bought a fairly high end (still under $100) battery charger/tender which also does battery conditioning. I have used it pretty consistently for maybe 6 months and the battery really seems to be getting and keeping its charge again (always over 12.8v when I check it after everything has spooled down).
I don't know why, but it seems AGM batteries don't get a full charge with my truck's power management logic on shorter, more frequent trips that is my use profile now. It will be interesting to see how long my AGM battery will last, now that I am getting it fully charged between runs.
In the end, I doubt I will spend the money on a super duper AGM the next time around.