I'm another that has no business giving advice on thinning the herd. I did cut back when I bought out the farm from my grandpa but I still have a dozen here and quietly have my eyes open for a middle aged youth horse for my kiddo
I think CCH said it really well and I agree wholeheartedly. Do what you know is right for you, not for anyone else. I know if I had to thin out here there are those that I absolutely couldn't part with and those that I would consider but wouldn't necessarily want to. Keep the ones that you have the can't part with feeling about.