
When a base is “abandoned”, all the doors and crates (and the loots) are accessible to anyone who will find it, and the base claim can be “claimed” by a different player who don’t have a base yet. After 3 days that no one is claiming the base, that’s when it would disappear.
I think it’s a cool mechanics that a base you abandoned could be looted, and even occupied by a new player. It’s realistic, adding to immersion. And it also gives a chance for the original owner to reclaim it past the first 7 days if no one else occupied it yet.
Maybe have some visuals of broken doors and walls, collapsed towers, etc.. to signify a base is abandoned. New occupants must invest new materials to repair the broken parts.

Yes. Would be cool fighting over a (decayed) base like in rust

I would not want to see any kind of general base decay system in Deadside, but having bases spend a few days in an open, lootable state before disappearing sounds so good. Even without any new claim/decay mechanics; just retexture, remove the doors, and make it destructable. Just for a day or two - after the claim has lapsed, but before it gets scrubbed by the server. Could add a lot of opportunities for gunfights out in the hills in what would usually be quiet spots.

^indeed. Instead of just looting villages, looting abandoned bases could become a thing. And as you said, increased encounters in base locations since players would be checking out bases if they are still active or lootable.