Regarding your reasons for getting a layback post, it's not all about cockpit length. When each crank is at 3 o'clock your knee needs to be inline or slightly ahead of the ball of your foot if I recall correctly. So too much layback could cause knee pain.
Back to the original topic, I've had a Twelfty for over five years and it's great. Sure the anodising hasn't lasted as well as that on a similarly aged Thomson but other than that it's fit and forget.
Each year I strip and clean the post and that stops it creaking for another 11 months and value for money is great.
For reference the Twelfty has 12mm layback and the Thomson 16mm.