Funny, I JUST set one of these up last night (haven't pitched yeast yet). However, mine was a pyment with 3 gallons of grape juice added in addition to 12 lbs honey.
Anyways, I "steeped" the wort with the cinnamon & orange (skipped clove, nutmeg, allspice) for 12 minutes. This was done right after taking the must off the heat, and covering. I could really detect the orange scent after that time, and hints of cinnamon.
I stole this technique from Malkore's "not-so-ancient" mead recipe. It seems to have worked very well, but I have no taste-test to prove it!