I have heard that of all the things that can break and mess up a bike tour that are amazingly light weight and cheap, seatpost bolt is near the top of the list. I cut a slot in mine several years ago, I might have suggested it on this forum. I think I used a Dremel Mototool cutting disc, not hacksaw.
I used to carry a spare until I realized that my stem cap bolt would be a good spare, quit carrying a spare.