@An Ankoù I don't think it's possible to replicate cask ESB in a bottle or keg for that matter, buy a bottle of ESB, it's not the same as cask, neither is keg ESB, and if Fullers can't do it I doubt anyone can. The life expectancy of a cask of ale, once tapped is about a week, largely due to oxidation and condition loss so the yeast munching away doesn't really come into play, cask breathers (aspirators) have greatly extended the life of a cask but you would still expect the cask to be emptied within a couple of weeks. it would be really interesting to see how long it would take for the flavour profile to change to a noticeable extent due to the yeast activity. Good luck with the F2, I suspect the residual 1968 will continue to create problems long term but time will tell.