At some point of course genetics and individual durability thresholds play a role, but generally it is fairly demanding for most guys to run over 120 mpw and then also do a lot of sub 2:19:00 Marathon Paced workouts all the time...so a higher percentage of "fast paced miles under 5:17 pace" is a fairly big injury/overtraining risk.
However for a 3:00 or even 2:40 marathon runner (who may be running say 70-80 miles per week) hitting marathon pace is much more manageable as velocity at Lactate Threshold is not as close to Marathon Pace velocity (and with this we assume that the sub 2:20 marathon runner has nearly maximized potential at the half marathon and run it very close to Lactate Threshold velocity....if they are at least a sub 1:06 type of runner).
Now I failed to qualify for the 2016 Trials (missed by 12 seconds at Boston in 2015 where I was 16th place) so I've for sure messed things up in the marathon a lot before....but I did run in the 2007 Trials (standard was only 2:22:00 then) and the 2012 Trials (hit the "A" standard of sub 2:19:00 and also hit a sub 1:05 half marathon). I've also trained with a lot of guys who ran in the Trials who have run in the 2:17-2:11 range (bascially when I was one of the slowest guys at Hansons-Brooks).
I'd say most guys for sure are running over 100mpw for weeks (if not months) on end. You can get some super talented guys that go sub 2:19 on less for sure though. When I ran 2:16:52 I probably averaged about 120 miles a week for 8 weeks straight with a high of 130....but in the 6 months leading into that I was coming off a 1:04:32 half marathon on about 90-100 miles a week most of the year and a lot of sessions at sub 5:00 mile pace.
Now you can read my "book" "Running For The Hansons" for some of our exact training in there, but I can tell you it was basically a lot of these types of workouts:
20-mile Long Runs starting at 6:15 pace down to 5:30 pace for most miles with miles 15-18 at low 5:00 pace...under M.P).
5 x 2-miles first starting at MP but then later on being 10sec/mile faster than goal MP. with half mile jog recovery (8-min).
3 x 3 miles (same paces at the 2-mile repeats pretty much).
8-mile "Tempo runs" starting at M.P. for the first 4 and then faster than M.P. for the last 4.
Then some 1000m repeats (like 8 x 100m) at 20sec/mile faster than M.P. with a 2-min rest.
OR 5 X 1600m repeats also about 15-20 sec faster than M.P. with a 3-min rest.
These harder workouts were usually every 3rd day (so 2 "Easy Days" in-between)..often on 10-12 day "cycles"
Of course those are all "bread and butter" type of marathon workouts and when you get into the nitty gritty of it the timing the execution really does matter (as well as periodization). Sometimes I got cooked in that program.
Even though I ran my PR in this program, I still consider my 2015 Boston (which was only 5-6 weeks after LA) on par as the best marathon performance of my life. I'd also usually recommend some 22-24 mile Long Runs (Hansons always cut me off at 20-miles for some reason and it drove me crazy).
There was also the infamous "16-mile Simulator" and 2 x 6-mile workouts...that we generally smashed and ran faster than M.P on...sometimes it was probably too much.
You could look into "Specific Endurance" sessions...longer efforts right around M.P. as it appears your speed is excellent and your mileage/volume have been excellent. If you did that 20-miler at 5:24 pace that is a very good indicator that you are pretty set already. Nice work!