Are there disadvantages to having him leading the armies?
There's no advantages really, other than the satisfaction of seeing your mighty leader at the forefront of the battles. Often the faction leaders start off as the best commanders so keeping their command rating high by winning battles can help secure a strong lineage, although really many more factors influence their offspring's traits. The disadvantage is of course there's more chance the poor blighter gets a blade lodged in his head and he takes an earlier than necessary trip on the Ferryman's boat.

Quote Originally Posted by Stuperman
Once generals marry, they need to settly down for a honey moon with the new wife. i.e. kids are much rarer for generals on campaign that arn't in a city often or for a couple of years at a time.

they will also get bad habits based off the buildings in the settlement, you might want to take them out a city every couple of years and have them build watch towers or something.
I'm not convinced that is the case. I've never noticed governors stuck in settlements gain children more than those out on the field. Births seem quite random. Obviously fertility traits help influence which of your family members are going to get a child next, other than merely boost the chances of having a child full stop.

As to bad habits in settlements, they also gain good traits much better by being in a settlement. You just have to make sure you keep them out of settlements that have buildings that encourage a lavish lifestyle or one of wantonness. Taverns and temples devoted to wine or love or fertility etc usually cause your governors to turn into drunken womanizers. Whereas ones that have temples to gods of war, academies etc often help create a strong leader. Actually in standard RTW, academies actually gave no benefits other than additional retinue characters. The Bugfixer and I think BI changed this, although the later patches might also have done the same. In any case, I'm happy to allow my generals to sit at home as I never have an abundance of cash anyway which gives them more bad traits.