Years ago, in the mid 80's, I filled out a float plan from copies I obtained from the USPS course my wife and I had both taken. Prior to leaving for extended trips, I never sent a copy to the USCG or HM - even though that was advised by our instructors. But, we gave a copy to a land-based family member.
Funny thing though, that was with a 25 foot boat - since then, we've taken much longer journeys in larger boats and have never filled out a FP. We do however, always announce our planned destinations and return date to marina friends, prior to leaving the slip.
True Blue . . .
sold the Nauticat