richard_new_forester

I heard a Tom Stoppard radio play recently: "Albert's Bridge". It features a large railway bridge which must be repainted regularly.

At the start the paint lasts two years and four painters are employed to paint it from end to end, taking two years.

In the play, they decide to save money by using new paint which costs four times as much, but lasted four times as long. The cost of the paint works out the same, but they can use only one painter, who will take eight years over it.

In the story, they forgot that a direct switch would result in some two-year paint being left for nearly eight years, and the unpainted part got tatty. Listen to the play to see what happened...

My question is, what should they have done? What would be the best way of switching from two-year paint to eight-year paint, without either leaving repainting too long, or painting areas unnecessarily soon? Clearly you'd need to keep some of the original painters on, but how many and for how long?