First off, I ran collegiately so I know some basics about training schedules and how workouts are structured, but I'm rather undecided about this topic. This is mainly because I haven't really looked into the exact research of the benefits of aerobic threshold intervals over a consistent aerobic threshold pace (e.g. fartleks or just plain hard running) and I'm not exactly sure where to find it. Right now I am training for a 15k in March.
I started running again in the middle of december at about 20 mpw up to where I am now. I've been using a Garmin 225 to track my mileage, pace, and heartrate (probably my first mistake). The closest track is about 20 minutes away right now and I just don't know if the time it takes to get there and back is worth the 'extra' benefit of doing 1000m repeats. I'm also in graduate school so I study essentially every day from about 7:45-5/6, so the time is actually a factor for me.
I started back in December running all my runs around 6:30-6:45 pace at 20 MPW. As I've gotten into shape I've increased the distance and pace. Im up to about 45-50 MPW running 6 days a week and now averaging about 6:05/min for all my runs. My normal day is start out and 6:20 pace for the first mile or so and then get into a groove at about 6 flat pace. I try to push my pace every day as a substitute for not doing any workouts so my heart-rate (according to the Garmin, when it is working) for most of my runs is between 170-180. 6 flat to 6:05 is a comfortable, but not necessarily 'easy' pace.
Yesterday I did 11 miles at 5:45 pace dropping a 16:45 5k in the middle. Would it be even more beneficial to start doing intervals at aerobic threshold? It seems like what I am doing right now is working pretty well, all things considered.