Originally Posted by chasm54

I'd be recommending 8-12 hours per week, not per month. About 80% of that at low intensities, zone 2 just below VT1 probably gives you the biggest aerobic bang for your buck. use the outdoor riding days for these long, steady distance rides.

Then once or twice a week I'd be using the trainer for shorter but much more intense interval sessions. If you look in the racers forum there's a sub-forum called "the 33 - road bike racing ". There's a sticky thread in there with a pretty inexhaustible menu of different types of intervals. Since you're familiar with power, you might find Friel's cyclists training bible, or Coggan's Training and racing with a power meter, a good investment.