So heres what we are looking at here:
The DHCP process within your RVO82 seems to be “quitting” after a certain amount of time. This seems to be ranging over a span of a few months (4-6 months) and power cycling kicks the DHCP process back in. Once the router has kept an IP for a distinct amount of time, it stops requesting for an IP (through the DHCP process) and it simply keeps it (like a static IP). We need to figure out if Cisco knows of any bugs that might cause the DHCP process to go dormant after a select amount of time and then kick back in once power cycled.