I'm a 14 level player,and,since I'm out of Cup and Ch League Competitions,
I've started increasing Friendly matches with my friends ,
I'd like to plan tournments in a more usefull way, but I realize that not Everybody knows how
Friendly matches DO NOT change the status (cards,injuries...) of teams invited,
but ONLY the one of the organizer.

If someone can't (or doesn't want to) take part on the match,just ignore the invitation,
and his/her team will automatically play the match with no effects.

Besides you can organize your matches only according to your friend's scheduled matches.

So,I think there's no reason to delete a friendship only for a friendly match you were invited,but it usually happens,so having nearly 50 friends is a good result for me.