As far as I know the only thing you need to do (provided you use the correct amount of vinegar, with maybe some salt) is seal them up tight. You might want to do it like you would canning your own tomatoes, or pickles. I wouldn't freeze it though. If you have too much for you to use, gift it to others that like it. Maybe make a few different versions (red, white, other colors) and have people try them.
Even though I've seen dates on the store bought horseradish, it tends to keep until you've used it up. If you do a good job of the canning, I would expect it to last at least a year. If you've not gone through it by then (or given it to those that will) then you need to either give it to more people, or start eating it more. :rockin:
Personally, I don't use enough of it to justify making my own.