There are many, many views on when, where, why and how to train.
The reason to build base is that you have allowed your fitness to degenerate; somewhat, during your off season. The reason for an off season is:
You have to de-train in order to re-train.
If you've been riding and racing 1000's of miles over the past 9 months, your body and mind need a rest from that.
Believe me, they do. You may feel good now. You may feel good after training w/o an off season for the 1st 2-3 years, but, in order to reach your full potential,
you have to bring It up slowly..It should take at least 5 years of training with solid scientific methods to reach your full potential.
If, you bring It up any faster than that, It (you) will not reach full potential; AND, it will not stay at its peak for very long.
Think of cycling fitness as baking a cake. If it rises too fast, it will get big bubbles and when you wiggle it, it falls.
If you mix it thoroughly with the right ingredients and bake it at the right temp for the right interval, it comes out solid with perfect form.
Now you can ice it.
Its all relative, base is no exception. So, after a 3rd year you may very well have more base mileage than you did before your 1st year.
Still, you want to build it, from what it is, to what it can be.
In my opinion, its better to err on the side of caution;
you wear a heart rate monitor and just do L1<>2 base work the whole off season.
Efforts will become more intense because it wil take more and more to elevate your heart rate to L1<>2, but, you will stay aerobic.
If you feel froggy throw in a few L3 building efforts. L3 efforts in off season, are mostly just to keep you from falling asleep on the indoor trainer or rollers.
Racing will give you plenty of L4<>5 time and if you have the blood volume, your body and mind will handle it fine and recover nicley.
If you have someone in whom you confide for advice, do as well as you can to stay fidel to their advice. Trying to piece together a program off the internet by use of advice from several different sources will probably not work very well.
If you don't want ther advice anymore, tell themso that they and you can move on and stop wasting time.
Notice the difference between a coach and a trainer.
Kompai,
Not Sure