If the permenant sensor lasts 5 year and the unit has a 7 year warranty, can I get this replaced every 5 years?

Thank you for your question. A warranty replacement can be fulfilled for the duration of the warranty, for this unit it is within 7 years after the date of purchase. If you have any additional concerns, please don’t hesitate to reach out to us at First Alert at 1 (800)-323-9005.