I know myself, and a few other players have also mentioned, tends to forget to check my boarding estate and kick horses. Also, admittingly, for awhile I figured it auto-kicked horses that no longer met my boarding rules. That being said, when it hits that I need to check it it's usually a bunch sitting to be kicked. I literally just had to kick about 90 horses on one account that no longer met my rules set. 

I think it'd be nice if it was built in to automatically kick them if possible, or if that'd be too much add a "Kick All" button that removes any with a click. I could understand this being one of those sub-tiered only things as mass actions are, but I feel like it'd be a nice addition. Especially for those of us that tend to forget we have to go do this by hand and end up with tons to kick. ^^;