I get that, I came home after a week in Moab to find my Dodge dead just sitting there... disappointing. Unlike my Dodge though when the welder is OFF there is nothing connected on the inside.
So far mine is one of the oldest built in 2017 (5 years old) and used heavily. Still working and charging fine. The manufacturers of the AGM batteries tell us we should have a usable life of 8 years under normal daily use conditions. Typically it's the depth of the discharge that limits the life span. i.e. you take a battery from 100% to 90% thousands of times, 100% to 50% hundreds of times or 100% to 0% like 10 times. In the case of a welder, if you get to like 50% battery capacity you're likely not getting a hot weld anymore so it basically prevents you from really DEEP discharging them.
Sitting on the shelf the batteries discharge about 3% per month so sitting on the shelf for a couple months is fine. I typically recharge after each use then lock it back up on the buggy which currently lives outside. If it's been a LONG while I'll charge the night before a 4x4 trip but with the knuckleheads I wheel with it's gets used basically monthly.