Originally Posted by Carbonfiberboy

Cutting through the possibility that your zones aren't quite right, try going by breathing instead of HR. I've been using HR data for 20 years, but I still prefer to go by breathing. You want to stay just at or a little below the first ventilatory threshold (VT1). So you start riding and very gradually bring up your effort while noticing your breathing rate. As your effort comes up, you'll start breathing deeply but slowly. Finally at some point you'll notice that your rate of deep breathing begins to increase rapidly with only a small increase in effort. This is VT1. Below VT1, you can speak in complete sentences with ease. Above it, you're down to phrases. A good way to tell is that at or below VT1, you can recite the alphabet. I can usually do one and a half alphabets. AT VT1, after the recitation I'll breath more quickly for a few breaths, but the recitation is comfortable.

But back to your question: I go by hours per week. I've had best results by using polarized training, that is I spend 80%-90% of my training time at or below VT1, and then the rest above VT2, which is defined by the point at which one begins to pant uncontrollably. I try to maintain that to some degree even on group rides by hammering the heck out of the climbs and then sitting in on the flats. I move right along on the flats solo at VT1, 16-18 mph. After a good group ride, I usually see the least amount of time spent in zone 3, with more time in both zones 2 and 4 and a nice chunk in zone 5.

Thus I never am "done" with base training. Base training is every week, all year. The difference is in early season I get even more base hours because I'm not limited by recovery from harder efforts. Try going out with only water and riding 2-3 hours at or below VT1. That really helps. Yes, putting in a lot of saddle time helps. That's possible because zone 2 does not require much recovery.