You can make anything go on forever - just look at the Spitfires still flying, some of them even older than the oldest trains on our network. But you have to treat them nicely, and through lots and lots of money at them. Some say that it was wrong of the RAF▸ to stop using them, and that the seats in the new Typhoons and F35s are much harder, but you have to move with the times.
Stick a couple of HSTs▸ in museums, ask the heritage rail sector if they would like one or two to restore and run (at 25 mph) once or twice a year, and move on.
Absolutely Tony. I fully expect a fair number will be kept running and preserved but you can’t keep all the power cars and coaching stock; some will end up being scrapped as sad as that is.