What version of DVDRMP are you using? What's the DVD size after merging 9 discs together? Are you planning on compressing to DL or SL?
Are you replacing the default
DvdReMake merge menu with the TMPGEnc menu? If so, did you follow this guide:
http://www.dimadsoft.com/dvdremakepr..._menu_full.php ? Play length of the motion menu should be retained. Check that the still time is 0 in the Programs pane.
Here are some more guides that may be useful to you:
http://www.cdr-zone.com/forum/post-31315.html#31315