Looks like I know where I need to focus my attention on and try and get in the “Mo' volume, mo' volume, mo' volume” during my longer weekend runs.
Not so fast. It would be better to get it in throughout the entire training cycle (week), no need (nor a good idea) to load up the weekends unduly. Keep the long runs at a healthy proportion of the overall volume, so that none of the rest of the training week ends up compromised as a result of overdoing it on any single run or workout. Same for any other hard workout throughout the week, killing oneself to the degree of sacrificing a day or two before or afterwards in the name of recovering from that workout is sub-optimal. It is the overall volume that plays the real role here, not any single run. Someone who could run sub-3 on 60 mpw seemingly already has sufficient speed, what likely needs the most work is the aerobic component, which relates to sustaining speed as well as using energy stores more efficiently. This can be done throughout training, with tempo runs, progression tempo runs, mp runs or segments of runs, strides, anaerobic threshold runs, aerobic threshold runs, etc. — not just in “the final 2-3 months.” The marathon has a 99% aerobic contribution vs. a 1% anaerobic contribution, therefore it should be obvious that the more aerobic development one achieves the more it will pay dividends in the marathon as opposed to working to develop something that is merely 1% of a contributing factor. This is not to say that anaerobic consideration should necessarily be ignored altogether, just that unless and until one maxes out one's individual aerobic volume then it should not be much of a concern.
If looking for a particular plan or program that pays heed to the true importance of aerobic volume and balancing the mileage intelligently between each run, the Hansons would be an outstanding place to start. Keep in mind that the sample training plan is dumbed-down to the level of the general RT readership and that it can easily be padded (eliminate the scheduled day off, perhaps add a couple of miles each to the longer runs and workouts, mix in 2-3 short recovery runs to add in doubles on 2-3 days, etc.) for those who are ready to progress further and develop beyond what that sample schedule would allow. One maxing out at 70 mpw need not put more than 18 of that in for a max longest run, one maxing out at 80 need not go beyond than 21 — just to address that one facet of the entire training picture.