Can I can chime in with an "impose it yourself idea". I know you shouldn't have to. But if you can PDF you files and make an imposition sheet suitable for your own printer then you can have an InDesign Imposed file to print out that is automatically updated every time you make a new PDF.
If it's 32 page saddle stitched, it's not that hard to do. Page 1 starts on the right and 32 on the left.
32/1
2/31
30/3
4/29
28/5
and so on.
The page pairs should always end up as 1 more than your page count. As you can see above, 32+1 = 33, 2+31=33, 30+3 = 33, 4+29 = 33 and so on
It's very very easy to impose. If it's bound then you can work in 16's or 32's, but only impose the first 16 or 32, then start at 17 or 33 for you next batch.
But remember this will only be for your own printing purposes, a printing company would prefer single reader pairs, not printer pairs. So always supply files to a printers as 1,2,3,4,5,6 etc. not 32,1,2,31,3,30,29,4 etc.
You'll save yourself a lot of time with this