When I am doing something stressful (like jumping or reining manouvers) I try to always use boots. Not that they have to have them, I just feel better knowing that their legs are protected from overreaches and strikes plus have just a bit of extra support that could help prevent a bowed tendon. I use them on Denny pretty much every time I ride because he has had numerous injuries to his front splint bones and I just don't want him to hurt them again while I am using him. I use them on my others only when I am doing arena type work (not very often) as a preventative. As far as boots go, IMHO, it is better to have them and not need them than to need them and not have them.