I would replace them all, you don't know who has access. Maybe some drug addict. Or the burglar cousin of the previous tenant.
I'd also want to be able to open the doors from the inside without a key.
Hmm, this got me thinking.
I'd LOVE to have a single (or perhaps two) keys to open all of the common door locks in my house: front door, back door, basement door, bedroom door, various closet doors, etc.
Any reason NOT to do that? Right now, I have four keys to get into the common areas of the house, not to mention the (non-attached) garage and other doors.
apart for the front and back door I don't see why you'd want to keep the other keys on you, e.g. leave the bathroom key in lock inside the bathroom, since it's meant to close yourself in the bathrooms, not prevent thieves from entering the bathroom when you're out of the house.
Regardless of that, in a house with like multiple apartments you can have keys that can open everything, just the main door, the main door and one apartment, or the main door and multiple selected apartments, whatever you want.
So you can do whatever you want.
If you keep all your keys on the same ring, there's really no reason to have different ones, if it's stolen, they'll get in all areas regardless.