veganjoggler, see my responses
in italics below:
1) Generally speaking, how long should each full session of interval training be? 10 minutes? 40 minutes?
I think this depends on where you are in the cycle and also which race distance you're aiming for. My guess is that you want to know what your marathon training intervals should be. For marathon training, I like to do between 2 miles and 10 miles, not including jog rests. So early in the cycle (12-16 weeks) I might do 8 x 400 meters with 1 minute jog recovery and late in the cycle, I might do 4 x 2.5 miles with 0.5 mile jog recovery.2) Can I do interval training the same day as a regular, steady paced run? And if so, before or after the steady run?
Yes, but I don't think it's necessary. I think you should go into a workout feeling fresh. Remember, workouts are also good for developing mental toughness. If you had a really difficult workout but you managed to hit all of your target times, you'll be able to reflect back on that when times are tough during the marathon. And it's much easier to hit the target times if you go into your workout feeling relatively fresh.3) How many times a week should I do interval training?
One or two, but I don't think you need to do more than one.4) For someone who already does 40 to 60 miles per week of running, which means about 5 to 6 days of running and one day of rest, and completed marathons, how long should the speed interval be? 1 minute? 3 minutes? And the resting/walk interval?
See 1 above5) Is it a good idea to do interval training the same day as I do strength training?
See 2 above. Although, you could do strength training after the intervals.6) Are there any Android smart-phone apps I can use to help time my intervals? Since I am a joggler, I need it to make sounds or beeps, since I can't always be looking at it. I already use Runkeeper, but I don't think it has this feature(I use the free service). It should be able to run while Runkeeper is running, without interference.
No clue on this one7) Is it a good idea to get anaerobic threshold testing from a lab or club to help me structure interval training sessions?
I wouldn't bother going to a lab. A club would be very beneficial for this. You could also go to this link (http://www.mcmillanrunning.com/index.php/calcUsage/calculate) to figure out what your times for each interval should be. You put in a recent time and a goal time, so you'll know where to start, and what to aim for.Good luck!