I recently brewed a Porter (AHS's London Porter mini mash kit) and added about 6 or 7 (I think) ancho chilis (dried) at flameout and removed once the wort was cooled. I just opened my first bottle last night after a few weeks of bottle conditioning/carbonating and it was missing much of the chili flavor. I'm thinking it may come back a bit after some aging because when I took a wee taste when bottling, it had the distinct raisin-y, mild heat, slightly smoky ancho chili flavor and scent.
Next time I would add a bit more chili at flame out (esp if using a low heat chili like the ancho). I wasn't really looking for heat, moreso the chili flavor. Another thing I would try is when taking a sample in the fermenter to add a chili-steeped-tea if it seems the chili flavor is not dominant enough.
Brews typically mellow out over time with aging so I would suggest, IMHO, to add a bit more chili than you would initially think.
I'll post the recipe when I'm in front of my brew-laptop later this evening.