Most of the marathon training advice I've seen calls for developing a base, then adding threshold training, then adding VO2max workouts during the final 10-18 weeks of training. I've been developing a base for about 6 months now, starting at 40 mpw and now up to 70-75 mpw with a 21-mile long run, but I have no plans to run a marathon for another 28 weeks. I initially planned to run one this spring, but decided against it because my body has responded slower to the training than I expected, probably due to my age (not 25 anymore).
My question is, would I be better off continuing with my current training for another 3 months, then adding VO2max workouts during the final 3 months of training as most schedules seem to call for? Or would I perhaps benefit more by adding some VO2max work now? For example, alternating each week between an LT run and a VO2max workout. Here's some quick reference info, along with a typical training week for the last 2 months. Also, due to work schedule, 75 mpw is typically the most mileage I will be able to get in. If I tried to double, it would require running at about 4:30 a.m. and limiting myself to 6.5 hours of sleep a night.
Age - 42
Marathons Run - 3, all in early 90's (3:21, 3:07, 3:07).
Easy Pace used to be 7:45-8:00/mile, now closer to 8:20-8:40/mile.
Current Typical Training Week:
Sunday - 20-21 miles easy
Monday - 6-8 miles easy
Tuesday - 6-8 miles easy; or 4- to 5-mile tempo (7:15 pace)
Wednesday - 14-15 miles easy
Thursday - 6-10 miles easy
Friday - Day Off (Usually work 13 hours on Fridays)
Saturday - 6-10 miles easy
I plan to run a marathon in 28 weeks. During the next 6 months, I will run other races, ranging from 5K to half-marathon, but I'm primarily focused on the fall marathon, so I don't intend to do any major tapering for any of the other races. Any input from experienced marathoners, particularly those over the age of 40, would be greatly appreciated.