Late to the party, but thought I'd add my 2 cents!
As Robert said, back away from the edge.

Also, like he indicated the goal is to get to the starting line strong and injury free! We'll all do it a little differently, based on our experience, physical health, mindset, etc. D
I agree with others that 20 miles is fine. Last year I completed the marathon with a LR of 14 (injury) and while this year I'm planning on doing 20+ (for my mental health), I'm not going to worry about things if I don't hit some magical number. 20 should be fine.
I'm also doing b2b, but not every weekend. That's also for my mental health--I need a break from constant b2b. And my b2bs aren't always SLR/LR with the SLR being 1/2 the distance of the LR. It'll vary, depending on my XT, how fatigued I feel. Sometimes I'll get the miles in without worrying about pace, and vice versa. And in some cases, my LR will come before my SR. And there are even days when the SR and LR aren't b2b so that I can fit in a local race or two. (Okay, so it sounds like I have no plan whatsoever, but I do.

)
You know what I'm finding makes the biggest difference for me this year in how I train. Prioritizing the XT, especially strength and core. Last year a back injury threw me off, and my back really hurt after the marathon. Poor (non-existent) core muscles.... so that's a priority to me even above b2bs! Take that for what it's worth.
Oh, and I think your plan for biking is excellent! Isn't Pat doing some of that?
Anyway, the REAL reason I dropped by was to say we're all in this together, and I just know you can do it! The Goofy will be filled with your WISHer buddies, and we're going to have fun together. Visualize a sea of lime green while you're training--the miles will fly by!

(Okay, so they won't really, but hallucinations on the training course do pass the time.

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