I took over 6 gyms and only got booted out of 1. I still regret putting my Typhlo and Kingler in though. And my Golem, would have been nice to test him vs the Jolteon solo raid. At least those rival teams' mons brought them coins. Next time I'll just put in weaker stuff I likely won't need anytime soon.
Niantic should implement a turf war kind of thing to reward for owning a certain number of gyms. It could function similar to the old 10 coins a day thing.