It takes months for gas to go stale though.
Just "don't charge" your PHEV once or twice, and you'll cycle through the gasoline. Pretend its an ICE vehicle about once every 3 to 6 months and you should be fine.
You probably have a road trip / beach trip where you were planning to use its gasoline tank anyway in that timeframe. You only need to travel ~300 miles to cycle through most of your gas tank.