if you follow the original recipe, it likely won't reach it full potential until it's 6 months old. imperial stouts like this one are like barleywines or big belgians - you brew them then you need to forget them for half a year (hence the importance of having a pipeline). the fact that it is so complex has so many things going on (coffee, chocolate, etc) further extends the amount of time needed for flavors to develop. you could start drinking at 2 months but don't be surprised if it tastes hot & alcoholic. it sorta defeats the purpose of making a big beer. if you need to drink something big in short order, consider an IIPA/DIPA.
alternately, you could try dialing down this recipe from it's projected 8+% ABV to something lower, like say 6%, by ramping down the malts & hops... but you're taking a risk there, since the recipe is balanced at its current levels. taking everything down by 25% will yield something close but the balance might be off but a 6% beer will be ready faster than an 8.5%.
but in a nutshell, if you want to drink something in 2 months you might want to consider a different recipe.
