Re: Boilers

As repards weather a life expired boiler kills the life of a locomotive I personally have a view that it dose not. Many locomotives had there boilers swaped around with those of class mates and spares and new boilers were constructed if nessersary.
In the UK a number of our locomotives have had new boilers fitted in recent years. Admittedly these are the older locomotives and they are greatly smaller than those in the US but these new fitts continue to happen. Both The Earl and The Countess at Welshpool are/have had new boilers in there recent rebuilds and the Ffestiniogs Prince is on its third! (1863, 192*, 1981) and posably more. This is however costly, but it is deamed nessersary to keep the locomotives running. To this end there are at lest three UK companys whos sole, or main, business is the construction of boilers for locomotives. To keep the order books full they also do contract repairs!
What would be better. Having lots of "original" locomotives with life expired boilers silent in sidings/museums or haveing a working steam locomotive that has many replaced parts, up to and including the boiler!