The greatest challenge is always in recapitalizing the fleet. That's an enduring challenge in all navies, because of the two points I mentioned earlier, one being the long time it takes to procure warships. Since it takes a long time, there never seems to be a sense of urgency, because a decision today only generates effect seven, eight, nine years from now. Delay is almost always possible in making decisions, because they won't cause an immediate effect. That's one challenge based on time.
The other is based on cost. Naval platforms being expensive, there is always an issue of fitting them into a program. The cost coupled with time means it's always easier in some cases to push things off just a little bit. That's why sailors tend to value a long-term plan that regularizes the acquisition, since it makes the coming to terms with a decision today for something that's going to generate effect a decade from now easier to deal with.