If you’re a professional, and you’ve raced more than 40 days in the last 9 months, then yes, 3 weeks or so off the bike makes sense. Your body needs a chance to recover completely before beginning to prepare it for your new season.
If you’re like the rest of us, and you have to plan your training around a full time job and family commitments, then it’s unlikely you’ve raced so many days and trained so hard that you need sustained time off the bike. In fact, taking more than a few days off the bike will required extra effort to recover the fitness you lose.
Training with intensity without a break for months on end can develop fatigue and make your training less effective, nonetheless. We use a technique, Training Stress Score (TSS), to measure the intensity of your training and ensure we hit the right balance between effort and recovery. However, unless you are training full time, you are unlikely to need an extended break!
In your annual training plan, there are periods of relatively higher and lower intensity, as those allow us to work on your muscular endurance and your aerobic efficiency, respectively. It’s all about having a plan designed to help you achieve your time-bound goals (see the post from 1 December, below).