I have a set of four Lifeline AGM's on Eventyr and have experienced a marked loss of performance. I contacted Lifeline a year ago and was instructed to equalize them at 15.5 volts. I did this with my Xantrex TrueCharge 40+ on the wet cell setting. I regained some capacity, but only temporarily.
In my situation, I'm living on the hook almost 24/7/365. I have solar and wind charging, but most days, I do not get back to a full charge. I run the generator on occasion but only for an hour or two a day. When it's running, I have two 40 amp chargers putting it back into the bank, but not to a full charge. Doing that would require five or six hours of gen running time.
I'm seriously thinking of switching to wet cell deep cycle batteries. It seems the value is there as well as the performance.
I contacted Lifeline on a warranty issue recently and they weren't much help. I had a casing failure and obvious leakage around one of the posts. I sent photos and a detailed explanation to them and had several conversations on the phone with the warranty rep. He basically told me that, yeah, it is a problem and we can send you a replacement for that battery. The problem with this, as I told him, is that one new cell in a bank of three older cells won't work. Further, I would be responsible for shipping the thing from California to St. Maarten. I was completely unsatisfied with this arrangement, but that was the end of our discussions.
Lifeline advertises as a premium manufacturer. Be aware that premium manufacturer and premium cost does not equate to premium customer service.