When do I Give Up and Go Home?

So I've been playing Die2Nite, and my second town seems like I can actually learn something from it. I've just begun autosearching.

So, is there a certain point at which a zone becomes depleted? I mean, should I come back after a certain number of hours to move to a new zone? Will I even be notified if the zone I'm searching becomes depleted?

I'm still not sure how many times one has to search a zone for it to become depleted, or if it varies from zone to zone; from past experience I'm guessing it's around three-four searches. If you're going to leave your session idle for a while, four-six hours is a good amount(two-three searches); however, you must beware of other players who might stumble upon the zone and search it themselves, causing the zone to deplete faster.

When a zone becomes depleted, the Scavenge Zone button becomes Scavenge Zone(Depleted), letting you know that the zone is depleted, along with a nice helpful purple icon above it confirming that it's not lying about the zone being depleted.

Note that depleted zones aren't empty; you'll still have a chance of finding common materials such as rotten logs and scrap metal to take back to the workshop with each search, just nothing special like drugs or chests.