Originally Posted by KrisZ
The VW Jetta I drove with a TDC rev matched all downshifts, so it should not be a problem...
The fact that a DCT rev-matches (all of them do) only saves the clutch(es); it does zero for saving the synchromesh.
All DCT's, i.e. from all mfr's, make their shifts "single-clutching" (so-to-speak, if you could liken it to a non-automated single clutch manual transmission). Now they are variously equipped with double-cone or in some cases (or for some gears... the lowest of the gears)- with triple-cone synchro's. However, they do not double-clutch like a skilled driver can, with a manual 'box (where the "to-be-shifted-into" gear is sped-up while in neutral, clutch pedal out, to perfectly match up the synchro splines.... so no- or very little synchronizer action is actually necessary). Little synchro-action, little wear.
The other thing that a DCT does - is the shift mechanisms move with lightning speed. So though the synchronizers are quite strong and effective, it's like every shift the transmission makes is a speed-shift. Can you imagine a manual transmission car, where every last shift is executed as a speed-shift... both up-gears and gearing-down (which is really hard on the synchro's)!
Now a certain amount of this duress, and the capability to withstand it, is designed-in. But what will the life-expectancy be with someone who aggressively downshifts (at considerable speeds) in manual-mode, all of the time?
For me, I will just continue to double-clutch down, and generally lazy-shift... to gain long life out of my manual 'boxes.