Roger, a full time RVer and AM Solar Partner, just proved how you can get seven years out of AGM batteries if you take good care of them with quality chargers.  Last weekend he replaced his four Lifeline GPL-6CT (6V 300Ah AGM) batteries with a new batch.  He has a custom battery tray made by our neighbor (Commercial Metals) for his rig, a 2005 R-Vision Trail-Lite 235S B+ (24′), that enables him to slide out the majority of his 400+lb system with a forklift.  This clever design makes system maintenance much easier (assuming he has access to a forklift).