With 98% +16, probably a tadge over 7 hr if you really wanted to. Back in 1978 at Sunny Scampton, the 617th Dead Dog Mob and the 27th Geriatric Boat Spotters competed to fly the longest Vulcan sortie... Whereas 'Sweaters', our boss, told us that he'd personally kick the ar$es of any 35 Sqn crew to waste flying time on any such stupidity.
Good man!