I think this is an initiative that could be sustainable over the long term if the Conservatives and Liberals can all agree that a viable ship building industry is something Canada needs. If the ship yards can be guaranteed x many ships over y many years they can plan to create z many full time positions in a region (NB, the Maritimes, Quebec) that could stand to have some more economic stability.
Most corporations replace and/or upgrade a portion of their capital assets on an annual basis. Asides from personal empire building and a lack of political will there's no reason the Navy and Coast Guard couldn't operate under a similar concept with a portion of ships being paid-off and replaced every 1-2 years.