I would say the ideal training for me would be to have been training for at least 20 weeks and build up to 80s or 90s in mileage. You want to have a least a couple 20 mile runs and should be able to do 16–17 miles at your goal marathon pace.
Life gets in the way, but finding a great training group is also essential, or at least it is for me. Doesn’t matter the distance — I struggle running alone.