I keep mine under the seat in the pilothouse. I advise people where they are before heading out, and I also assign one to each person. In an emergency, I don't want people trying to work out which lifejacket fits, - especially important with children or large people.
We use ours regularly. As a rough rule, If the seas are less than 2-3 feet its optional. 3-5 feet, I insist on it when on the foredeck. 5 feet and over - and we also wear a harness to go forward.
When I'm singlehanded the harness is used more often. I don't want to see my boat sail/motor off into the sunset without me.