Seasonal anaerobic development? First, it depends upon some key factors. Foremost, it depends upon the individual. What works for Jo man not work for Sam. Jo may have a high percentage of fast twitch (type 2) fibers and therefore could handle far more "anaerobic" work than Sam. It really comes down to the percentages of fast twitch fibers you have inherited from you parents, especially your mother.
The second factor is the event you are going to focus on. Is it the mile or the marathon? This makes a lot of difference. Why? Simple - event requirements!
In the case of the marathon, the worst thing you can do is overdevelop your anaerobic capaicty (more specifically your anaeorbic power). If you do so when you are aiming for a marathon you won't perform well. You'll burn carbs way too fast and you will erode aerobic efficiency. You'll be relying on your anaerobic capacity to provide ATP. For example, a 3 hour marathoner aiming for 6:52 per mile would use about 2-3% anaerobic, on average, as they run along IF THEY OVERDEVELOPED ANAEROBIC CAPACITY (instead of just under 1%, which is ideal for a 3-hour runner).
At about 18 miles the inefficiency of using 2-3% anaerobic will catch up with a marathoner and start to cause early fatigue. By 21 miles their pace will slow by 30 or more seconds per mile. They have burned up the carbs from their legs and liver. By the end, they fall apart, running a couple minutes a mile slower than their intended pace.
Now, on the other hand,a miler will need to develop more anaerobic capacity and power than a marathoner. If anaerobic capacity is low but aerobic capacity is high, a miler will run a good mile but finish with the feeling that they "just couldn't shift gears." That is, they couldn't dig deep and get some more power from their legs. This a reality of under-developed anaerobic capacity and power.
Often milers, however, have overdone their emphasis on anaerobic development (whether it was due to running too many fast reps and sessions or from neglect of aerobic capacity during the weeks when anaerobic reps were being emphasized)so they end up being unable to "hold pace" in their mile race. They "die," in other words. They can go out quickly the first 400-600m, but they slow considerably afterward. *How badly one has messed up the ratio of aerobic to anaerobic development is shown where and when an athlete "dies" in his or her 1-mile race.
Ask the questions: Did they slow after 600m? Did they slow on the third lap and couldn't get anything going until the last 200m? Did they die at 1200m or just afterward?
If a miler dies in the third and or fourth lap of a mile race and they have been doing "anaerobic" reps in training for a few sessions, then it is the aerobic capacity that is either under-developed or wasted away from neglect.
Now, if someone WHO HAS A HIGH PERCENTAGE OF SLOW TWITCH MUSCLE FIBERS will need to know right up front that they won't be running many anaerobic reps or many sessions fast if their goal is the one-mile race, even though the event requires close to 20-25% anaerobic contribution, on average. It would be a big-time mistake for a "slow twitcher" to do plenty of anaerobic reps an sessions, period, regardless of the event. He or she would fall apart when doing many anaerobic reps!
The miler type who has plenty of fast twitch fibers will be mistaken, similarly, if they do plenty of anaerobic reps as they prepare for a marathon. The event duration is so long that overdeveloping anaerobic capacity is the factor of greater consideration and takes precedence over personal muscle fiber makeup.
So, there is no pat answer. It depends upon the person and the event they are participating on as to how much emphasis should be placed on anaerobic development. This is where the art of coaching comes in, whether self-coaching or from another person.
I sometimes greatly regret giving out information like this. Why? This stuff ends up being put on some other websites from those making money off coaching. Yes, I do make a small amout of money from coaching, too, but it is my material, inspiring people to hire me!
Perhaps this makes me seem like an unfriendly person for saying the obvious. But, I feel a need to say that others are fakes in how the present themselves as originators of material and methods. It bugs the hell out of me, to be perfectly frank. (I can imagine how ticked off Arthur Lydiard would be at times when others would use his training methods and claim they were the ones responsible for success of runners. Also, I can see how Mr. Lydiard would be ticked off when people would claim they are using Arthur's training method when in fact they were bastardizing it in both content and method).
Never the less, I hope my explanation does some good. Hopefully it clarifies a few things for you and gives you some direction. Remember, there are guidelines which work for most of the people, most of the time, but YOU ARE UNIQUe and require adjustments related to your personal constitution and race goals. If you can't figure out those things for yourself and implement them, then get a coach to observe you and be your objective guide. Tinman