How long can a creditor hound you for an unpaid debt?

There is no time period in which a creditor/collector must cease attempts at collecting a valid debt.

All US states have statutes of limitations for debts owed. The SOL is the time alloted for the creditor to file suit against the debtor to collect monies owed. The expiration of the SOL is not always a guarantee of not having to pay a valid debt(s), certain circumstances are applicable.

It is the legal right of the debtor to inform the creditor/collection agency that they do not wish to be contacted about the debt either by phone, email, postal service, etc. If the debtor wishes to take such action he or she should send a "cease and desist letter" to the creditor(s) requesting that collection attempts should be ended. The correspondence should be precise and sent via registered mail with a return receipt requested in case proof is needed of the action having been taken.