If you have friends that no longer play, they can remove Solitaire Tripeaks from their Facebook account, so they don’t appear in your friends list. But they’ll probably need to know how to do that.
I have several that don’t play anymore, but I continue to ask them for coins, instead of taking the time to uncheck them, which I did at first. Tripeaks is set up to allow you to ask for help from 50 friends at a time. If you have more than 50, do this, and then it won’t matter how many friends you have: