Exactly how bad is it to be over the demesne limit? Is floating 1 or 2 above while you wait for your heir or a betrothal to come of age or to finish your schooling okay, or will that come back to bite me later? There are only so many celibate courtiers I can give these counties too.
In addition to the negative opinion there are events linked having to many I have seen... I think it can lead to the "stressed" trait among other things...