Great stuff, Tarheels, would love to have you guest blog on Springfield Brew Crew sometime. The great thing about beer is that we all have our own way of enjoying it. I have had aged Imperials that are fantastic when fresh, but -- in my opinion -- even better with age on them. Its a matter of what I like opposed to what you like. I'm not sure I agree with you regarding several points, but again, beer is something different for eveyone. I merely state my thoughts and let folks go from there.
However, the question of storing beer upright or laid down is one that requires more discussion. Lying a beer on its side for storage can, after a period of time, impart cork flavors into the beer. This can lend off flavors to your brew and that is never a good thing. Beer stored on its side also causes a greater amount of the beer to be exposed to the small pocket of air at the top of the bottle, while rare, this can contribute to a greater rate of oxidation and again produce off flavors. Many important brewers will tell you, corked beers in particular should be stored upright.
As far as the question of why to store beers; beer, like wine, gains complexity as it ages. Even a highly-hopped DIPA will benefit from aging. If, that is, you do not mind that it will lose some of it's characteristic hoppy bite. The right beer, aged properly can go from splendid to sublime with flavors so rich and decadent you will be hard pressed to call the liquid beer anymore. OíHanlonís Thomas Hardyís Ale will continue to evolve for 25 years or more. Yes, it is a Barleywine, but it is exceptional. Rogue's XS is an example of a Russian Imperial Stout that gets better the longer it stays in the bottle -- I have a bottle of the 2008 just waiting for the right occassion to open.
So, if you are a hop-head and want the full on assualt of the hops -- and, believe me I do love that -- then drink your IPAs, DIPA's, and Imperials as soon as you get them. However, if you want to explore the other flavors that can be drawn out of one of these brews, be patient and let it age for a couple of years. You might be glad you did!
Every once in awhile someone will come on BeerAdvocate/RateBeer and say they've had good bottles of one year Hopslam. I don't doubt it, but I have not enjoyed any old DIPA. Yeah the Thomas Hardys vintage stuff and JW Lees barleywine are pretty much expressly made for aging and are weird exceptions. They are thinner, sweeter, and essentially unhopped compared to American barleywines like Bigfoot. I love the older JW Lees/Thomas Hardys stuff but they are very thin and sweet and honey forward and intentially show loads and loads of oxidized character which is nasty in something like Bigfoot, but works for the sweet, thinner English barleywines.
But to counter you sideways vs upright discussion, I think you'll find there is really no consensus on best way to store them, but I can assure you that at all the lambic producers in Belgium and in the best beer cellars in the world like Akkurat in Stockholm, Kulminator in Antwerp, De Heeren van Liedekercke outside Brussels; all the 750 corked and caged lambics are stored on their side. I've toured all of those cellars. At Cantillon they will store 150 bottles sideways on top of each other.
Main reason is to keep the cork wet. The cork may impart "corked" flavors to the lambic just like in wine, but that is an uncommon occurrence since cork is chose for wine expressly to expand when wet and to have a neutral taste. A "corked" off flavor is not a guarantee. It is actually the exception to the rule. For example, one of the largest wine cellars in the world is at Bern's steakhouse in Tampa, FL. They have 500,000 wine bottles in their cellar: http://www.bernssteakhouse.com/BottomMenu/WinesSpirits/tabid/58/Default.aspx
ALL of these wines are stored sideways including something like a Petrus 1964 that may be worth $3,000.
Again reason one is to keep the cork wet, expand, and not allow oxygen into the bottle ruining the wine and beer. Second is your point about the air. If the bottle is upright, then the carbon dioxide pocket is in direct contact with the cork separating it from outside air. If the cork gets dry and shrinks, then that CO2 pocket can leak and O2 can enter and ruin the beer/wine. If it is laying on it's side, the cork is wet, expanded and tight, and the CO2 pocket is laying against the glass in a long, oval bubble.
Your original reason for yeast sedimentation doesn't matter. If the bottle is laying on it's side for say 2 years, yes there will be a thin, long layer of yeast particulate along the lengthwise of the bottle. Big deal. When you are getting ready to serve the bottle (beer or wine), you put it upright in the fridge or whatever and spend a day or two letting the yeast settle back down around the punt of the bottle of the bottle.
Now if you store a wine/lambic for a very long time on its side, that yeast particulate actually gets "glued" to the side of the bottle and is called "DIESEL" at least in lambic speak. And this will not move whatsoever. Start pouring it upright and it will not mix with the bright flavors of the non yeast muddled beer/wine.
Here's more on "corked" off flavors, which in 4,000+ different beers I've reviewed, I've NEVER come across. http://beeradvocate.com/community/threads/beer-connoisseur-cellaring-article-question.20158/
In that discussion, yes there is no 100% agreement but the head lambic blenders at Drie Fonteinen and Cantillon store them sideways and that is their entire livelihood. Why would they jeopardize their entire business if "corked" flavors are as common as you think they are?