I'm planning to store the corrected address along with a timestamp indicating when I performed the validation. Once an address has been validated, should I treat it as good forever, or is it wise to re-validate after some amount of time has passed? If I should re-validate, how frequently do you recommend?
Addresses themselves don't change too frequently. Street names don't get renamed too often and only on rare occasions do house numbers change. However, new addresses are added to the USPS delivery database every day and ZIP code boundaries get realigned as needed to accommodate changes to delivery areas. Remember, a ZIP code is a mail delivery area, not a neighborhood, city, or county boundary. Also, people move in and out and an address that was previously deliverable may now be vacant.
In order to keep your address data up to date, we recommend performing address verification at least every 90 days. This will ensure that you have current data.