The problem isn't that things decay too fast, it's that it's all a mystery and very unclear, and the repair mechanic is very finicky to say the least. Some walls I can repair, where others I can't seem to target to do so. Same with doors and metal shards.
An easy solution, and this is most likely probably already planned (it is alpha afterall), every building piece in the world (like doors) should have ownership, and when you look at the door, wall, crate, etc, it should show health next to the circle along with current health, with the option to repair as is done now (and have it actually work all the time)
That would be nice. But my issue still stands.. I have a job and I am not home to repair my home. Sometimes I am away from my computer a day or so at a time. I think 3 Real time days seems fair for decay.