Currentlly I'm playing teclis and while I like the army abilities the scholarly tome provide, setting the cap to the same amount you need for unlocking the army ability is too low. After you acquire a few loremasters of hoeth, you will almost always have tomes that go to waste due to this cap. You also have to pause your research and spend it immediately on an army ability research if you don't want any further tomes go to waste.

The worst case scenario happen in the events where you either get tomes at the cost of a debuff or spend tomes for a buff. Since you can't choose a "Do nothing, nothing happen" option you are stuck with two bad options when you have more than 75 tomes: Either get the full debuff while getting less tomes or spending tomes for a buff you might not want.