As far as I know gthe longest used gear would be a ship which came into british service courtesy of being captured at trafalgar, and was used there after...
Latterly she was a coal hulk during ww1, and a barracks during ww2, she was sadly sunken by your RN in the late forties/early fifties I believe.
However I cannot now remember her name.
The stern decoration has been kept at a naval museum I believe, as has her statue thingy at the front ( sorry brain freeze):???