X2
I have a suspected MG pos flock, after reading that it's rare for backyard flocks not to have it I don't feel bad not depopulating. Any new birds would just get it again. I do make sure any birds I sell are not showing symptoms -therefore they aren't contagious- but overall I just don't worry about it.
Quite a few of the ones that are hatched from my eggs never catch it.
ETA: I'm not sure how it is in your area, Saris, but around here most flocks are in poorer health than mine. Of course, there's a few well cared-for flocks but not many keep birds for anything other than eggs/meat.
Having rare breeds would change the playing field tho.