I've trashed chains in 1000km.

I've had chains last 5000km.

There are so many variables here than no-one can tell you how long a chain should last.

Throw a bit of beach sand in there and that chain will be toast PDQ. Cross chain or have an issue (like one that would bend a hanger) and that chain could be toast PDQ. The OP should stop listening to the geniuses on BF and just measure the damn chain. It ain't rocket surgery; Either it's worn or it isn't. Let that be your guide and replace if needed.