While the recipe and gravity play a big part, I'll argue that your carbonation level and cellarmanship play an equally big, if not bigger role.
Writer's Preemptive Strike: It's been a while since I was in my 20's, so I seldom brew above 1.055 and very rarely cross the 1.060 threshold. I happily acknowledge that bigger beers do require more conditioning.
That said, I used to subscribe to the notion that a porter, especially a porter with a decent dose of brown malt, required at least a month to relax, better two. It used to drive me nuts how I would consistently keg a beautiful porter and then it would become quite unpleasant for a week, then gradually improve. It made no sense.
Eventually, while chasing the ideal bitter, I learned to keep my UK ales off the gas and barely carbonated. At serving time, I hit them with enough gas to liven them up as they pour, then immediately dumped the gas, via the PRV, once I'd finished the session. UK beers have a reputation for being warm and flat for a reason--they taste better that way because they're designed to taste good when served warm and flat.
Wow, did that make a difference with porters! I quickly learned that brown malt wasn't, in fact, a surly malt that needed extended aging to chill out. Rather, I had just been hitting a malt that will not tolerate any kind of carbonic bite with too much gas. With this new method of cellarmanship, I'm able to go grain to glass within a week and my porters are as well-behaved as any other UK ale.
This technique works equally well with N. American stouts/porters, except for the fact that you're serving a lot colder.
Also, remember that you want your beers that rely upon roasted malts to mash at pH 5.5+. I've found it makes a real difference.
That's what I've learned about this. I hope you found it useful.