Comment by astura

Yeah, you gotta determine what is more likely

1) the landlord didn't change the locks between tenants AND there's a great "key copying conspiracy."

Or

2) There's an emergency requiring your landlord/maintenance to enter the premise when you aren't home.

I know which one I find more likely, but you do you.

OTOH Probably most landlords won't mind you changing the locks as long as you give them a copy of the key.