With the large amount of area that are secluded and abandoned with no other buildings or zeds around there are tons of things you can do. Evac shelters are plastered all across the world, usually far from the horde. Go read a book next to the computer console, it never turns off and provides steady light. Work on making a shelter, go on a night raid, work on your driving in an open field, train tailoring on some clothes you otherwise wouldn’t have. Get skills up that you dont usually have.
Throwing is a nice little time killer, so is archery which also raises firearms. Raise some hell, get drunk, smoke weed, break into a lab, break into a military outpost. Read play boy and spank your monkey, capture a zombie for experimentation or cook crystal meth. Chop down trees, burn down a city, work on making your own home in the wilderness and many many more things I’ve forgotten. OH, work on your truck, repair your truck, blow up your truck, blow up yourself, drink bleach.
I mean, in my shelter I’ve got an entire workspace near one of the computer consoles and it’s my arts and crafts area. I’ll spend an hour making socks then turning them into rags so I can raise my tailoring and a couple hours before getting my focus to unnaturally high levels and I know that I’ll have to dig like a thousand trenches for my perimeter to be safe. The way I was thinking of doing it was a large ring with enough space for my truck to pull out of and a smaller ring that I can walk out of around my base. That way with both rings of pits, filled with spikes and the ones that hug right up against my base, I’ll have three chances to kill something that cant fly, should it encroach me.