Seth;

We count the descent time in to the training total time. You’re right that they are different but the downs build a special kind of strength that you need in the mountains. Ultimately you need to just be consistent in how you count your training time. And, understand that the times given for the Z1-2 aerobic workouts is a sort of middle of the road guesstimate. If you have more time or more training background feel free to increase the volume. As long as you are recovering well more is probably better.

Scott

Seth,
TO answer your example-question: For a 2 hour workout like this I would break it down as follows:
15 min slow warm up (zone 1)
1-1:15 up
30-45 min down.

The time ranges would depend on the terrain and speed of descent. Don’t worry about being over-precise here. The important thing is doing the workout and if it ends up being 1:45 or 2:15, it’s not the end of the world and the exact optimal amount is really hard to pinpoint unless you’re working with a coach, then that’s their job and their judgements are based on loads of experience, which provides them with a good feel for what the right volume is. Get within 10% + or – and you’ll be doing super well.