FiOS router includes ability to release the DHCP lease.
1. My Network icon on top row
2. Network Connections in left window
3. Click on Broadband Connection
4. Click on Settings button at bottom
5. Click on Release button on DHCP line about 2/3 of the way down
6. Immediately power off the router or disconnect it from WAN link. Otherwise it'll start DHCP all over.
Just where you would expect to find it.

DHCP lease is typically based on MAC address/device name. Firmware update doesn't change those, so you shouldn't need to release DHCP lease.
Replacing router is different situation. Releasing DHCP lease from old router ensures new one gets online immediately.