The 99 comes form the Video Title Sets (VTS) limitations in the DVD spec.
The full DVD spec allows 99 VTS per disk. And it allows 99 chapters (PGC blocks) per VTS (timeline). But Encore uses "auto VTS" and allows only one timeline per VTS.
I do not know how this may affect number of menus. Menus can reside in VTS and Encore's limit may or may not inhererntly limit that. But I suspect that because you have no control over placement of menus in the DVD structure, they are only at the disk level (VMG). I cannot find a number limit to those menus. (There is a 250 menus limit to the number of menus allowed in a VTS, that, again, i am guessing is not allowed in Encore.)
In any event, I have never authored a menu with over 100 menus!
So at the end I ended up with only 70 menus, so I can`treally confirm if there are numericcal restrictions, anyway, thanks for the insight.
Ha, ha! Come on. Add another 70 so we know! Congrats on finishing a "big" project.
The Authoring is not the issue, but the testing is pure Horror!