With Teeth: took at least 3 years to write (possibly more, but that's how long we were aware of it)
Year Zero: took 3 years to write, as it was written during tours and used ideas he'd had during WT
Ghosts: the entire concept was to write as much music within their set time frame. More Ghosts would logically follow suit in that fashion - but Ghosts and the TRAR scores are LITERALLY the same team, so if you want more Ghosts, go back to the three scores (and maybe try Atticus solo too)
The Slip: again, the concept was to do it quickly (and totally recycle old tracks, like Letting You and Demon Seed)
The Slip and Ghosts are anomalies in the NIN catalogue, look at his entire work history, not just 4 out of 9 releases.