My inflator hose fell off twice when getting into the water right after a BCD service when I was a newer diver. The first time, the o-ring fell out into the water. The 2nd time, the o-ring was salvaged for a moment, then lost as the assembly was being screwed back on (I learned not to replace it while in deep murky water, and to keep spares).
An instructor who was on the dive advised me to not service my gear so often and "if it ain't broke, don't fix it".
When I complained to the LDS that it was the 2nd time the inflator hose fell off right after service, they said it was my responsibility to ensure all the valves were finger-tight before going diving - even after service.
Anyway, I learned to check my valves and connections regularly, if not before every dive.