Nothing wrong with having a healthy sexual appetite; I always say.
Is It Bad To Always Be Horney And Want To Lick Feet?
No
Heck yea
I don't think it is if that's what someone is into, doesn't hurt anyone (except diseases and things if more than feet are involved and as long as you aren't cheating on your significant other to get your fix) and there are plenty of others out there. Pretty sure that's called a foot fetish.