I've ordered a sample copy of ST18 from Lulu. The point is to see the thing as an entity - not just proofing sheets of printout, but looking at the booklet as a whole and seeing if it 'works'. It's very hard to judge.
I think I got lucky with ST17, which was a last minute 'help, I need a printer' job. I feel I dodged the bullet, somewhat. So this time I'll try to be a bit more careful. With luck I'll see the sample copy this week, sort out any problems, and have ST18 ready for posting out by mid-October.
That, at least, is the plan.