major tune up and a carb rebuild is when i would start and keep your foot out of it. Keep it at 50-55.
I rebuilt my carb and did a major tune up and i am getting a little over 16 at the moment but i got a light foot.
I keep mine in a 5 gallon pail.
I don't flush since my stuff is clean i use Rotella ELC Nitrile free and distilled water. it stays clean and doesn't turn to rusty sludge like conventional green.