In reply to The New NickB:
yeah I'd just do some stretch, balance, roller work.
But running wise I'd make at least one run ~2hours, runnable miles, so not 2 hours of fell running (walking), so at least runnable trails..
I'd separate your efforts by a day if possible.
Also whats 'steady' and whats 'fairly fast', in terms of your marathon pace?
I'd be tempted to throw in tempo or MP efforts, 3-5 miles, with 1-2 warm up cool down.
But not sure if thats 'fairly' fast.
Generally I'd dump as much other stuff as possible..
But if anything I'd add 30-40 mile road rides.