Just rest a couple of days before the century. Do some stretching and limbering up a couple of times a day, but avoid weight bearing exercises or aerobic stuff.

Tapering is for athletes who train almost every day, several hours a day. When I was an amateur boxer training all out for multi-day tournaments, sure. We'd taper a bit starting a week before the tourney, after a lead up series of weekly bouts over a few moths. But for younger athletes one or two rest days before a competition is good.

Over-training can definitely hurt an athlete at a high level of competition. Former heavyweight boxer Evander Holyfield was notorious (other than for PEDs) for over-training. He was always fit, never fat, never slacked off. But he'd occasionally, almost inexplicably, gas out midway through some difficult bouts. Rumors behind the scenes (usually leaked by trainers or cornermen and gym rats with inside knowledge) said Holyfield was prone to over-training.

It doesn't apply to us mere mortals who ride 2-3 times a week for an hour or two, whether intervals or other. At 61 with oh-kay health and conditioning I wouldn't do any interval training the week of a long ride, especially if I wanted to ride fairly fast and finish well before deadline. And I'd take two rest days before the event, just stretching. I'd even avoid long walks. But other than that I wouldn't make any significant changes. But that's me. Other folks might prefer more rest or less.

Here's where I see a lot of amateur athletes (and even some pros) get into trouble, in cycling, running, boxing, anything...

They have a lot of pent-up nervous energy and try to burn it off too close to the actual event. So a day or so before the competition or event they're in the gym doing full workouts, then messing around with various physical activities, sometimes at night, basically leaking energy rather than resting for the event.

One of my friends has become pretty competitive in crits and cyclocross. She has a coach, she trains hard, is getting stronger. But she was disappointed with a fourth place finish in a race where she could have been on the podium, and just a middling finish on another race. I follow her Strava and the night before those events she was out after 9 pm on casual bike rides for 10-15 miles, socializing, drinking beer. And the morning of the event she was on her indoor trainer, working out, not just warming up. No proper rest days or prep.

Sure, there have been and are some much younger, fitter athletes who can get away with that, but by our 30s we don't have the kind of excess energy to burn and still do well the next day or so in competition.

Another example was Phil Gaimon's recent KOM attempt in Colombia. Not only no KOM, he bailed out. Very unusual for him. But he had a valid excuse. His Colombia visit video wasn't just bike riding but a mini-travelogue, and better for it. The day before the KOM attempt he hiked in the mountains. So he started out with dead legs.