I recently did my first Century. I'd done plenty of Metric Centuries over time, often as part of extended tours with full camping luggage, but had never done a 100 miler so decided that would be a good "life in the old dog yet" activity for my 50th birthday recently.
I've done little touring since we adopted our kids and what there has been wasn't far, but I've got basic cycling fitness from just getting about by bike. I built up the miles over the space of a few weeks, but I also did shorter hacks with plenty of hills and I pushed myself a bit up them to get my climbing muscles in to trim (nothing too Nairo Quintana, I just pushed at it rather than drop a gear and amble), not so I could race around the final course but so I could do it without having to go in to the red (my eventual route is http://gb.mapometer.com/cycling/route_4396679.html
this one, you don't ride 100 miles around here without any hills unless you want to lap a very restricted loop, and I didn't).
Buildups started with a 40 miler (first time on the 'bent in a year, seemed easy at the time but could hardly walk the next day, hmmm), then a couple of 12 mile local loops with hills (once with my wife, once solo), 40 miler with hills with the local CTC group, 20 mile higher intensity with bonus hills, 50 miler and then what turned in to a 60 miler where I hadn't had a plan in mind and just went where the wheels led me. The aftermath of the first excepted, these all went very well and my final buildup was to be the week before, doing 80 miles round my planned course to recce the bits I'd not visited before and then taking the train home the last 20. As it happened I felt fine at 80 miles, and having planned it with a fairly flat final 20 west to east with the usual prevailing winds that day I just carried on and did it a week before I'd planned. Once my legs were used to keeping going it was mainly just doing it for longer.
Whole thing, including stops, took 10 hours. I wasn't in any hurry (one of the nice things about the recumbent is I avoid the aches that limit my upright rides by time). On the actual ride, conscious of a long way ahead, I never pushed in to the red (aside from the very final hill up to my house) and I never had lactic acid to come back and haunt me as a result. Fuel was a good breakfast, stops for coffee with ice cream (20 miles) and cake (70 miles), some wraps I'd made for a packed lunch, a couple each apples and bananas, a small bottle of juice and a supply of Emma Pooley's flapjack recipe (use grated apple and condensed milk as a binder rather than sugar and butter, and add a supply of raisins). I took plain water and drank less than a litre, at my touring intensity I seem to generate water metabolising fuel and it's stopping for pees more than being thirsty that's a problem.
I was tired at the end, but not trashed, and wasn't stiff the next day (in marked contrast to the day after the initial 40 miler, so getting your legs used to just chugging away hour after hour really does seem to do the job).
Weather was okay, though not perfect. Got drizzled on for about half an hour and the coastal section had a bit of a nasty againsterly, but nothing that decent kit couldn't see off. I carried a waterproof jacket and a set of tools/spares (none of which were needed).
One of the main take-aways was that although I really enjoyed the actual ride, I also enjoyed the training rides a lot. Think of them as part of the enjoyment process and make sure you have fun on those, and the final route just gets to be the icing on the cake.
Often seen riding a bike around Dundee...