I'd like to thank
@cosmicbike for setting up the challenge this year and keeping us in order, and progress monitored.
I'm fine with the rules and the current interpretation thereof.
The purpose of this challenge is to offer riders the opportunity to share (with others making the same effort), concentrated in one place, their 100+km rides with the threshold challenge being that a 100km ride must be completed in every calendar month, and the pleasure of knowing that one has self-set a significant challenge and completed it. We should take care not to dilute the challenge. The 100km ride should be a 100km ride plus and completing one of these per month requires (for most) deliberately planning and riding one. Two 55km rides (or a 65/40, or whatever) separated by a day's or a night's work, or a night's sleep are two rides, imo, and neither are 100+km. A ride with a train journey (or even two) embedded is still a 'single' journey in my eyes. The train journey is being integrated to allow the rider to get where he/she needs to get to, or to offer better roads and thus a better ride. I confess in the past to doing 55km to our Wednesday evening pub meet, and another 50km afterwards (back by one). For me this is a 100+km ride, even though I've been in the pub for two hours +. The Imperial Century challenge 'no stopping at home' is there (imo) to deter/proscribe the 'do 85km', back to home for a meal, 'do another 80km' cunning plan. For the metric century challenge I think doing a ride with a meal or whatever stop at home mid-way through is fine, although part of the attraction of 100+km is that it gets one out a distance from home or the start finish point (as does a 'committed' train journey early on).
Where does that get me? I wonder whether a time limit of 3 hours (stopping or training) might be a reasonable definition of when a single ride becomes two.