Speaking purely from my own experience here with my own 2 T&S lenses, the 90mm and 24mm, the problem in using tilt for landscapes is the difficulty of moving the components in the landscape, such as trees or any tall object, to fit the new tilted focal plane. Consequently there is a danger of getting parts of the image, which might normally be reasonably in focus, suddenly out of focus in a surprising and unintended way. Furthermore, the small viewfinder of the 35mm format doesn't help. It's not always clear what parts might unintentionally be OoF, so there can be quite a bit of stuffing around involved.
The problem is worse with the TS-E 90mm because of the longer focal length. In a sense, there's a Catch 22 situation here. Using tilt with the TS-E 90mm is of greater benefit, if you can get it right, because DoF is shallower and there is more to lose by stopping down to f16 and f22 because this is a sharp lens. Using tilt with the TS-E 24mm is easier but mostly not necessary because such a wide angle lens has great DoF in any case. I would have no hesitation in using f16 with the TS-E 24mm if getting maximum DoF was an issue since this is not a particularly sharp lens. In fact, now that I'm using a 5D, I should probably be using f22 in circumstances where I used to use f16 with my D60 and 20D.
That might be my next lens test, comparing TS-E 24mm sharpness at apertures from f8 to f22 .