from the Lifeline technical manual, latest revision:

"Conditioning should only be done when the battery is showing symptoms of capacity loss due to extended time in a partial or low state of charge condition. This could be caused, for example, by low charging voltage for an extended number of charge cycles, or by repeatedly charging to only 90% state of charge."

I took a look at Morgan's Cloud blog, they make a blanket recommendation that batteries should be equalized once a month. This might be good advice for flooded cells, but not for AGMs. If you are charging them to the point they outgas (and thus require ventilation), you will ruin them in short order: the electrolyte lost cannot be replaced. They should be "conditioned" (equalized) only when absolutely needed. If you charge them properly, that would be rarely or never. Morgan' Cloud admits that they recharge only to 85%. Under that usage, they would be far better off with flooded cells. The guy from Lifeline is saying in effect, if you abuse them, then equalize them regularly to try to mitigate the abuse. But it is best not to abuse them. I have three large banks of Lifeline AGMs (the boat, an RV, and an industrial lift). They are 6, 8, and 3 years old. All have been properly cared for and are not in need of replacement. If they are drained at all, I try to bring them to full charge at least once a week. They have never been equalized. I did finally replace one in the truck camper at 11 years.

Both AGM and gel batteries need very careful control of charging, including temperature compensation. If you don't have a good charging system, then stick with flooded batteries. They aren't the greatest thing, but they do take a lot of abuse and neglect which will ruin other technologies. As the guy on Morgan's Cloud suggests, it may not be easy to charge the bank fully if you are not at a marina. I accomplish this either with a long engine run for other reasons (no wind day for example), or by running the alternator early in the morning to bring them to 90% or so (which also freezes the holding plates in the frig so it does not run that day), the letting the solar panels finish them off over the day. You need a fairly large solar array to do that. A wind generator would do the same thing.

Despite all that, I think when I replace the Lifelines it will be with lithium iron batteries. Recharge times are much faster, no partial charge issues, and much greater real capacity in the same space/weight. Their higher cost is mostly offset by the larger capacity and a longer predicted life.