Re: care and feeding of wooden weapons
Standard lemon oil works fine for me. Once a day for a week, once a week for a month, once a month for a year, as needed thereafter. From time to time, maybe a quick lick and a promise with 400 grit sandpaper if needed. I've had warpage problems from standing weapons on end, but in each case, that was also associated with a wide lateral variation in the grain of the wood from which the buki were made.
I haven't broken a bokken in over a decade and have a couple of working bokken that are closer to twenty than ten years old. YMMV.