Mex, there is no "hype". Nobody ever said that AGM last longer given same abuse as flooded. Also, any battery will shorten its life A LOT, if routinely discharged to 30% SOC with occasional dips to 10%. When people pay 20-30% more for AGM than flooded, they are trying not to subject it to such conditions.
Lifeline is one of the best AGM, and costs more, and I recall on that boating blog a while ago - when it was free - that expected duration was 2-4 years if charged to no more than 85% SOC and equalized once a month. Equalization is called "conditioning" in their manuals. Pretty wide range, as you can see. There was no number of cycles given.
