Thanks for writing in to us with your questions.
Picking a starting volume is kind of a trial and error experience. Look at your over all last 6 month average training volume and start with 50% of that is a nice conservative estimate for starting volume in a new cycle. If you feel like the previous load was too light then maybe start with 60-70% of the previous 6month average.
It is much easier to scale up the volume after several weeks if it feels to light than it is to realize too lat that you started off too ambitiously and have the wheels come of 4 weeks later.
There is a significant risk of just such a ting happening: Your motivation is very high now to start training again for the next goal race. You’re feeling recovered and ready to jump into training. The natural tendency would be to come out of the gate too hot. In your case that might look like starting at 40-45miles/week. But where is that going to put you 12 or 20 weeks later. You need to leave room for the progression.
Err on the conservative side. We rarely here from undertrained athletes (those who wished they’d trained more) and we frequently here from overtrained athletes (those that wish they’d trained less).