Microsoft may shit out a new toolkit every other year (which is a shame, they should be fixing their existing stuff instead) but at least they maintain them for basically eternity. You can pick up anything and it'll be there for years to come (though not everything may be bundled with the OS forever - IIRC some less used some are downloaded on demand, but still the applications do not break).

(though personally i mainly trust core Win32 as everything else is built on it and because of that it is the most likely to remain stable)