I guess it turns into a cost benefit analysis where you have to compare maintenance to demolition and land value. Beyond a certain point that estimate would be

I guess it turns into a cost benefit analysis where you have to compare maintenance to demolition and land value. Beyond a certain point that estimate would become less predictable. But the design will have margins of safety that increase predictability. A client buying a bridge or a skyscraper will probably be making a long term investment and want predictability.