I have one ESG 6GFM250 8D AGM (250AH) which has specs for "standby" and for "cycle" use. After about a year of RV type cycling like 50-90s it started to act up. It appears to have internal damage to its plates, and operates more like a 125AH battery at two years.
IMO this is more of a "standby" battery, but it doesn't tell you that.
I have had better luck with a pair of 12v 100AH AGMs which claim to be true deep cycle, but also have the specs for "cycle use" and "float use". After three years they are losing capacity quite a bit, so they don't seem to last as long doing my kind of RV work as regular flooded batts despite costing twice as much.
I am going back to Flooded 6s which I know will last me at least 5 years from when I had them before. I do all the good things and moreso for the care and feeding of my batteries, so it was not a case of neglect.
1. 1991 Oakland 28DB Class C
on Ford E350-460-7.5 Gas EFI
Photo in Profile
2. 1991 Bighorn 9.5ft Truck Camper on 2003 Chev 2500HD 6.0 Gas
See Profile for Electronic set-ups for 1. and 2.