I don't recall where the rule is found, it may be in the customs regulations, but I recall that there is a maximum length of time a US registered plane may remain in Canada before either having to be imported, or flown out. I faintly recall a friend a long time ago, owning an N plane, and deliberately entering and leaving Canada with it for periods of time to conform with the regulation. NAFTA may affect this, as I recall N jump planes operating in Canada, so there may have been changes in the rule I recall. Until certain, it is wise to be suspect of a plan to operate N in Canada indefinitely.