I've been doing steady mileage exclusively all year because I'm trying to build a big base before doing speed/hill sessions as per Lydiard.
The LSR debate is a strange one because when you read Lydiard, who was supposedly responsible for this theory, he encourages runners to run at their best aerobic effort depending how they feel definitely not slowly.
For me this invariably means a steady run which gets faster at the end but still aerobic. The only 'slow' running I do is a gentle 3 miles with the dog each morning on top of my other training.
I haven't done any speed work or ran really fast during my long runs but I definitely feel fitter and faster. I imagine speed/hill sessions will just sharpen up this fitness ready for those short summer races.