One thing that I have notice is that V&V only appear and/or evolve when the heir is included in a stack of several units that does not include the king or a general with more stars.

This means that:

- an heir/general with a good command rating but a bad vice (drinker, chinless, strange) should not be put in a stack with other units unless you want the vice to become worse (alcoholic, odd number of toes, unhinged loon). Of course if you do so you lose the chance that he might get a nice V&V (gentle knight, famously brave, etc.) that would counterbalance the bad one. The thing is that given sufficient time you are sure that the bad vice will get worse while you have very little chance to get a brand new one that will make him better (especially once you are the dominant faction since it seems that at that time you are doomed to get more and more bad vices). It is also necessary to make sure that such heir does not inadvertently the "leader" of a stack (when the king dies, if you retrain his units in a castle that has a garrison, etc). In such case the game seem to love to take the opportunity to increase the bad v&v immediately.

- an heir/general with good vices can be left in a stack in order for his v&v to improve but there is always the chance that he might randomly pick a bad one. It seems that you stop getting new v&v once the heir/general has about already 5 or 6 (when he reaches that point he only gets the one that are attributed a a result of your actions such as scant mercy, builder, steward, good runner, skilled def/att) Some good vices such as "numerate" will turn into bad one if they evolve to much (avarice) but my guess is that its worth it.

Once you get the dominant faction, it's usually a good move to leave all you generals out of any stack in order to avoid that they become crippled with bad v&v. You basically see that you are winning the game when almost all the v&v you get are corruption related or worse. I do not always do this since it takes a little flavour out of the game, all general remaining exactly the same the whole game ...

Basically, my view would that in order to get the most efficient result (I have not said the most fun):

- you should leave good heirs/generals in command of their stacks until you become the dominant faction;
- you should leave good commander with bad v&v out of any stack;
- utterly crappy heirs and generals can be left in a stack at all times since they can probably only get better with a little luck and since it does not matter if they get any worse...