Hi from Alaska. I'm 56 y/o. I quit smoking and started running in 2004. My first races were in 2007-I did a 5K (19:26), 10K (40 flat) and then a December (Las Vegas) marathon (3:32). I have never run a half. I couldn't really do many miles because I have tibialis posterior dysfunction. I deferred my BQ to this year. I have to do lots of physical therapy and orthotics/shoe tricks to be able to train regularly. I did see that my 5K predicted a better marathon. I needed endurance so I got a HR monitor this year and ran on grass in flats at my MAR for months...pace improved. I am now doing hilly routes every day, still aerobic. I have averaged 60 mpw for week for a couple months, hit 70 a couple times, long runs up to 24. I run outdoors-so heavy clothes and snow/ice have slowed pace, I just watch the HR effort, staying close to MAR (131).
I do fartlek now and then-short enough to be alactic. I think I will have solid aerobic fitness for Boston. What would you recommend between now and tapering 3 weeks out? Long intervals (e.g. 2 miles)? Fast finishes to medium runs? And if I add those elements, do I bring down the overall miles?
Thank you for any advice you can offer.

First, you have been putting in a lot of miles and long runs so you should be prepared to handle the distance easily. + hills to prepare for heartbreak.

I believe that you can keep the mileage where you are and add in some faster pace running. I would encorporate some speed once a week into your training. Up until five weeks prior to the marathon I would alternate between running marathon pace (MP) runs one week then threshold runs the other week.

I would run the MP runs on the same day as your long run, encorporate 10-14 miles at your MP in the middle of the run. On threshold runs, run at your 1/2 MP (estimate from calculators found online such as mcmillian) for approximately 40 minutes during one of your weekly mid distance runs.

With 5 and 4 weeks left you could either run a couple track workouts, say 6 x 800 meters at 5K pace, or continue with the MP pace and threshold runs.

Last three weeks, fartleks once a week during the runs.

If you feel any aches and pains I would reduce or stop the speedwork through. Better to get to Boston healthy than be fast and hurt.

Thanks Deely!