Particularly when I was first getting going, I didn't appreciate how important an aerobic base was. It just can't be emphasized enough.

If (and this is a big if) you keep training reasonable and varied, and don't do a huge number of races, life will take care of the breaks for you in the first few years; holidays, summer vacation, Etc. That's also assuming you take the advice about rest days. But if I had to nail it down it I'd advise the rest week(s) around the time that you get up two days in a row and feel that getting on the bike is a chore, or you're going to a race not because you want to, but you feel you have to. Or you you do a week where you never feel fresh.

Kinda blasphemy, but racers (reluctantly raises hand) tend to feel the solution to feeling poor mentally or physically is to do the stuff that makes us feel poor a lot more or a lot harder.

+1
I found this to be true for me as well. Between work, family, life, etc., EVERY DAY there is some good reason to blow off training; being accountable to a 6-month plan made it much easier for me to choose to get on my bike instead of (insert alternative). Maybe this is more characteristic of us older beginning racers who have a lot of other things going on in our lives? My first season racing, I made a plan in January to peak for a stage race in June (as much because I had to schedule vacation days as for any other reason), and had my best results of the year at that race, so peaking even as a beginner isn't always totally pointless...