You have the exact same issues. Different cases have different magnet styles and materials utilized, individual watches have varying degrees of decay to their magnetism. If you don't have the correct original specs for the reed switches, you are starting off at a bad point of reference. And of course, not many have invested in the equipment that allows for measuring the button magnets' strength in a repeatable fashion, for a good frame of reference. And of course, your setting magnets start into a whole another can of worms.
Probably my biggest concern about programmable modules (versus dedicated clock chips), is how often/frequently/easily could their programming get wiped out? I believe reprogramming them on the module is not feasible.