Well, first, you probably don't want to store your homebrew on it's side like you would wine. The sediment would settle along the side, then it would get disturbed when you set it upright to open the bottle.
As for lifespan... it really depends on the beer. Hop aroma and flavor tend to fall off over time, so a nice hoppy IPA isn't going to age very well long term while something like a stout or porter will handle it more gracefully. Higher alcohol beers tend to benefit from aging more than lower alcohol beers. Many barleywines aren't even worth thinking about until they're approaching a year old.
Temperature... many beers need some time to bottle condition before they reach their prime. Conditioning at warmer temps (not hot, but not in the fridge either) makes the process go faster. Once a beer has peaked, refrigerating it will help slow the process.