Deirdre/Sean:
Dunno if this helps but this is what I'll be up to....
After doing FLM (my 3rd mara), I'll be doing the same as before:
By the end of May I would have built up to my first proper long run of 20 miles. I'll be doing 3 long runs a month for Leicester in October and my last long run will be done a month beforehand for a nice early taper.
I find the 1 week in 4 break does me the world of good and so far have not yet burnt out. I usually get in 10-12 long runs before a marathon and my times are tumbling nicely (3:58, 3:41, 3:38 FLM in heat, sub 3:30 is next target).
The 3 long runs a month will be slightly different: 20 miler road race pace followed by couple of easy days as that's hard going, 22 miler middling pace off road and 24 miler slow pace.
I'll also be banging in a 8-10 mile tempo run with club, speed/hill session with club, fast 10k and recovery run each week. As I'm starting early, there's a contingency for the odd slack week if I'm tired or heaven forbid, if I get injured (touch wood, haven't yet).
Good luck to you all whatever you end up doing, and here's to more PB's! :-)