The resources refill very slowly on junkpiles; if you take 1 and move and don't overuse the pile it will regenerate by the time you accidentally hit that spot again

If you have a lot of people using the same small JP though it will deplete.
I know we have 2 big JPs on our land and I harvest each over every other day and only do west 1 day and east another
so i only have a chance to hit the same spot once every 4 days

we have maybe 6 deadspots on our pile but thats mostly from unauthorized people or new clannies who didnt get "the talk" yet