I have trained about every way I can think of. I believe what has been most beneficial over the years was weekly miles. The more mileage piled up the better the end result tended to be. The easiest way to achieve the mileage was 9-10 runs a week. After your body gets used to it, then the speed you run those runs tends to increase, but depending on the season doesn't really have to. You have to build the big aerobic engine. I don't care if your running 5ks or ultras the same principle applies.
I also think it's important not to drop this big engine into a body not ready for it. In words, don't go from 30 a week to 60+ right away. The body needs to adjust to the demands as well. When you can get these two to synch together you have a good thing going. This is the best way to get ready for any season.
For ultras, I don't think it is necessary to run 3-4 hours every week on this plan unless your doing races off 100k+. If you like do it every other or even every three weeks, just so you keep your mileage up. Shorter runs of an hour done quite a few times a week tend to be done at faster paces and your recovery is faster. At 50, I just don't recover enough on 1:30 runs like I used to. I tend to try and get to the point where I work up to 2 hours Saturday and Sunday. The rest of the week the goal would be to do 7-8 runs of 50 minutes to 1:10. At least that is what I would like to get near this winter, though I may stick to back-to-back 1:30s over the winter with an occasional long run.
If you can come into February-March with this under your belt you can make the adjustments you need to have a successful season.