It varies greatly with how you use/abuse your batteries. Many times the abuse is inadvertent - at least in my case.
I typically get 5-7 years out of the batteries in my cars, never less than 4.
I trashed the battery for the John Deere tractor in 6 months - left it in the tractor in the winter after I bought it, not realizing there was a parasitic drain. I did the same thing with my first pop-up.
On the second pop-up, I went through a couple of Group 27/29s in 4 years before I realized how much battery capacity the heater needed for 9 nights at Lake Tahoe.
Having thought I learned the lessons from the past, on my 2014 A122 A-frame, I had the dealer install a 2nd battery when we took delivery. Unfortunately, I did not catch that the WFCO converter would not go into trickle mode, causing one of the batteries to fail after one year. The failure ended up damaging the 2nd battery.
I replaced the two Group 24 batteries with Interstate GC-2s from Costco. I also replaced the converter and installed a cutoff switch so I wouldn't have to mess with connecting/disconnecting the batteries. With those changes, the GC-2s were going strong after 4 years when I sold the camper this summer.
I have installed the same GC-2s in the new A-frame. Since I was alert for the issue, I found this WFCO converter won't go into trickle mode, either. So I have disconnect switch, PI converter, voltmeter, voltmeter switch, and switch for stereo lined up for installation over the next month or so. I fully expect to see 5+ years out of these GC-2s barring something stupid on my part.
2019 Flagstaff T21TBHW A-frame
2008 Hyundai Entourage minivan
camping Colorado and adjacent states one weekend at a time