Hey, Coal..i do boot & saddle repair,,,anything you put on your boot's that seal's the leather( schlac's,,tent water proofing,,etc. )will cause the leather to crack ( not a good thing),,but a good saddle soap ,will keep them soft and help shed water. Just ,apply a good liberal coat ,,and buff. And ,,,yes more than once a year ( lol). A zipper can be put in the "back" of the boot w/ a flap to cover the zipper,, just a thought.
Hootmix.