So with some micromanagement you can have even more than 10 companions in your party but you have to be careful not to piss them off. First my relations with her dropped to about 30-35 but then it slowly rebounded and stabilised around 60. For example I have Ymira, Matheld, Lezalit and Alayen in my party right now meaning that Ymira has one friend and two enemies. My own personal experience is that even 2 dislikes and 1 like can be manageable, too.
It's not significant enough to require any additional micromanagement or anything, so I'd consider these absolutely stable. In Mount&Blade you are not the only hero. The two-way arrows indicates companions that like each other, which can help balance dislikes, increasing the effective limit. However, note that it is possible to keep a hero in your party along with someone they hate if you balance. One first must be aware of which hero hates which other heroes, as these conflicts will decrease morale and make it harder to keep your chosen heroes from leaving the party.
The only difference from the traditional 8 companion builds is that this has companions with 1 dislike and 1 like and your relations with those will hover around 80 or so instead of 99. If you wish to maximize your number of companions, you can choose 2-3 from the top circle and 4-5 from the bottom circle that are not touching. The following are tactical uses of Heroes from Mount&Blade and Warband that will allow one to optimize their party. There is a safe 10 companion setup and several ones with 9.
