Thanks for your responses, guys. Upon further research I've decided that what the folks brewed up at Dogfish Head Brewery is closer to an Ethiopian honey beer (t'alla) than a honey mead (t'ej). Two months conditioning after fermentation is probably appropriate, although the stout will condition for about six months beforehand before I blend them together.
Both will have an ABV of about 9% which will definitely make this a winter sipping beer.
It's interesting to note that the recipe given in "Extreme Brewing" for "t'ej" uses a mead yeast, although I have also heard from other brewers who suggest an ale yeast instead. There was a Discovery Channel show a while back about how DFH brewed this beer in about eight weeks (!) in time for the 50th anniversary of Miles Davis' "Bitches Brew" album, but commercial breweries have tricks and techniques unavailable to the home brewer. They considered using raw, unfiltered honey at first but figured out that it wouldn't dissolve easily in their equipment, so they ended up using a small amount as a nod to authenticity but made up the bulk with orange honey.
The "Extreme Brewing" recipe also recommends pulling about half the volume of beer out, three days into primary fermentation, and boiling for 15 minutes with 9 oz. of gesho. Cool beer and add back into the primary fermenter.
Traditional t'ej recipes call for boiling some of the honey with the gesho and the leaves (forgotten what they are called) to bitter the honey. The gesho acts like hops and presumably boiling the gesho isomerizes the acids much like you do when you boil European/ US hops.