That Horween horsehide is really freaking tough - so any leather conditioner will pretty much work. Some guys use Pecards, some use Neatsfoot. You can even pick up regular Kiwi mink oil. You only really need to condition the leather after it gets really wet, or if it's looking beat up. Horsehide can stand up to all kinds of neglect and abuse.
I can attest to this as well. I've had the horsehide boots for over 3 years now and wear them a lot during winter as well as even during the summer when I go on trips where I'm going to be walking a ton just because they are so damn comfortable for that. I've used nothing but Pecards on them maybe a couple times each year and they are holding up great so far.