Maybe if you are talking about an Imperial Stout, or some other high gravity version of the stout species. High s.g. recipes often benifit from a long aging period, but for most standart beers much over a month is not necesary. And always keep in mind that the one feature that degrades the most w/ time is the hop aroma and flavor, but since stouts are rarely high on either of those, a bit of aging is probably fine (I am soon going to be drinking a batch of stout I bottled 2 months ago, and am really looking forward to it!
O, guid ale comes, and guid ale goes,
Guid ale gars me sell my hose,
Sell my hose, and pawn my shoon -
Guid ale keeps my heart aboon! -- Robert Burns