Suzuki 40hp EFi service
It's each to their own really, 20hrs is nothing.
Personally I change all oils and filters (except HP filter) on my outboards at the start of every season.
I used to change impeller every year but do it every other year now.
I don't winterise either, just start it once a month and get it up to temp. You can get some cracking days in winter so I see no point putting boat into hibernation.
There is a place on this planet for all of Gods creatures.........right next to my tatties and gravy.