Chinooks = Hospital beds
From talking to people at'the 'home of the Chinook', they are like hospital beds. Its not the lump of metal that's the issue, its all the support staff and facilities that go with it, to make more of them into usable entities that is lacking.
Even if you could walk into a Boeing Vertol showroom and pick up the keys to a shiny new Chinook, you would still need to recruit and train all the people needed to keep it in the air.
Some years ago, an article stated that on the then current information, the Chinook would be in service for 87 years before being completely phased out (albeit this was refering to service with the US military, who had a head start). Any guesses on today's estimate?