Does it have to be an exact pace, or can it be an effort?
Because about 30 seconds/mile slower than current marathon fitness is a pace that feels great and I can run almost every day as long as I take occasional days off and my total volume isn't too high. And that pace would also let me have a pretty good time running half marathons and marathons (although, since they would have to be that pace, that wouldn't be true racing), and actually let me race short ultras if I ever wanted to.
I think that's my answer: current marathon pace +30s/mile.
