Seems I'm never specific enough in my language, but what I MEANT was that the threadless HS are easier to achieve initial adjustment and will stay correctly adjusted LONGER (which I contracted to "longevity") than conventional HS...and that is just my opinion based on limited experience and conjecture. Here's some more conjecture and opinion: the bearings and sealing mechanisms in many (but not all) of threadless HS are superior to most (but not all) conventional HS, and this will promote comparitively longer service life...note I only have TWO of my bikes (and only one road bike) set up with threadless HS and stem...all others are still high-quality conventional jobs, so I'm no fanatic convert.