Rekeying changes the pins inside the existing cylinder so it works with a new key. The lock body, knob, and exterior trim stay. Replacement swaps the whole hardware. Rekey when your existing hardware is good condition and recent — $25-$45 per cylinder. Replace when hardware is worn, corroded, or you're upgrading to a higher grade.

Rekey on every change of occupancy — moving in, after a break-up, after a contractor or property manager change, after losing keys. Replace exterior hardware roughly every 10-15 years even without incidents — pin springs weaken, weatherseals fail, and the whole assembly gets sloppy.

If you've ever lost track of who has a key — old roommates, ex-tenants, contractors, property managers — yes. Restricted keys cannot be duplicated without your written authorization and the original key card. For a single-family home, $200-$400 once buys real key control for the life of the hardware.

Most. The standard cross-bore (2-1/8") and edge-bore (1") spacings on North American doors fit nearly all retrofit smart locks. The exceptions are fire doors with concealed hardware, mortise-locked doors (need a mortise smart lock), and very thin doors under 1-3/8". We'll measure on the install call before quoting.