Interesting you advocate speed and hill work, I was going on the basis that slow and steady mileage will be more beneficial?
Early stage should be base building, lots of aerobic volume at easy pace. Occasional hill or speed work is OK, but very light. Better than pure speed work would be some strides or surges, short enough to not stress you but fast enough to get a strong leg turnover. About 3 months out you can start adding some quality runs. 800m and 1 mile repeats, and lactate threshold runs. I woudln't go too hard on these, and do 2 quality runs in 10 days rather than 1 week. Taking cut-back weeks after 3 weeks including quality. The key predictor in performance will be your run volume (and not overdoing the bike), but some quality runs will improve efficiency and speed a little. It is run volume and quantity of long runs that will get you to the end of the marathon in OK shape. The speed work will make you slightly faster, but with that comes a risk of bonking. Of course if you kept the same pace as if you didn;t do the speed work, then it will help you get to the finish more comfortably and reduce bonk work. Basically run volume lets you run and run and run, efficiently and with less distress, quality runs might make you 5-10 seconds a mile faster but that comes with a greater risk of failure unless you kept the original pace. Furthermore, the quality runs don't make up for lack of run volume. More harder/faster runs doesn't replicate what can be achieved with run volume. However if you are extrmely limited on time then more quality work will be better than no quality and low volume. Which is why it is a double win to get run volume in early, and then as you get closer to race day when cycling and swimming are taking up more time and recovery, then fewer, shorter but faster runs like a tempo run can help.
EDIT: Part 2
I'm not a triathlete but did train that way for a while and have several dedicated IM friends, some with sub-10 hour finishes. In the early stages (e.g. 6 months out) when they have high volume of easy running, the swimming is focused on technique and some hard intervals, but total duration is not huge. The cycling similarly has high intensity, doing FTP building work blocks. Since the swimming and cycling have high intensity, you definitely don;t want the run to have high intensity. And since the swimming and cycling are shorter higher intensity , there is more time for runnign and long runs. As they get closer the swimming and cycling includes longer race paced efforts.. E.g. 3000-4000m swims, 6 hours cycle rides. When those start spearing in the schedule there is more recovery time needed and overall less time for running, and it is too much to do a 20 miles run and 6 hour cycle ride just few days apart or same weekend as would often be required. Well you can of course do this, but the recovery time increases a lot and so does injury risk. So as cycling and swimming increase in volume they start reducing run volume, and that is also when some quality/intensity in running pays off.
General run fitness and aerobic performance in running takes a very long time to build, and is based on high volume easy pace. The good thing is this base aerobic fitness will also remain for some time even when volume gets cut back. Slow to gain, slow to loose. And also near unlimited potential, you just keep gaining and gaining and gaining. In contrast, The higher intensity run workouts lead to fairly rapid gains in performance (speed and efficiency), but are also more rapidly lost when training intensity is reduced, and there is a lower limit on gains available within any 1 cycle. So doing too much intensity too soon wont gain you more performance, just higher injury risk and burnout. A shorter period closer to the race is when higher intensity runnign has the biggest advantage.