Bolding from me for emphasis, because I don’t think this can be emphasized enough! 4 Dopeys under my belt, plus more other multi-day challenges than I can count, and I swear every training cycle, I tried something in a b2b2b (or b2b2b2b) simulation that would have been miserable during the actual races: poor shoe choice for that day, a pair of tights that were fine for 3 miles but I hated after 18, learning that yes I really did want to start with gloves on with the temp under 60º, even if it meant discarding them 2 miles in (which sometimes meant needing multiple pairs of cheap gloves for a multi-day challenge), discovering that I craved a Pepsi/Coke/Sprite around mile 20ish, finding that I needed a plan for dumping Tailwind out of a tiny baggie into my bottle with a strong wind blowing, etc. Not once have I not learned something new that would help on race day by testing things in training!