The military have a saying that no plan survives its first contact with the enemy. I have a policy that 'bicycle' and 'schedule' should never be used in the same sentence, probably not even in the same chapter. Also, I find that I enjoy being in a new place, not just zooming through it. As a result, I try to set an objective, and also have a bailout option or two, in case of rain, headwinds, etc. Sometimes, rarely, it even works out the other way around and I end up going farther than I planned. I also camp a lot, so I can set up my tent for lodging where evening overtakes me, again, rarely.
Thus, I'll spend time with maps and list all the campgrounds and inns, motels, B&Bs, etc. and have a list of check downs if progress precludes achieving my original objective for the day. I also try to read as many descriptions of other people's trips on that route as I can find to get a sense of where to stay, and where to avoid.