Excellent post and the advice goes for any battery system you install, wet cells as well as AGM or gel-cells.
Most of the pulse chargers will work for a short time, but they may not address the real problem of VRLA (AGM and gel-cell) batteries. These batteries will tend to dry out when they are cycled too deeply, charged with too high of voltage, kept at a high temperature and charged, i.e. everyday life on a boat. And since they are sealed there is no way to add the water back. As pressure increases within the battery with excessive charging and/or high temperature, the valve (Valve Regulated Lead Acid) will vent the pressure, i.e. hydrogen, to prevent damage (this is the way it’s suppose to work). With the hydrogen vented it’s eliminated from the battery environment and so cannot combine with the oxygen (via a catalyst) within the battery to maintain the water level. Hence, dry batteries, dead batteries.
None of my customers (telecom companies) use a pulse charger. They have tried them and concluded they don’t work. They just replace the batteries after fiver to ten years (and that is on 20 year batteries), more often if they are in harsh environments.
A dead AGM battery is a dead battery and should be replaced.