I came across this counter-intuitive tidbit on Wikipedia:
"While most wines can benefit from lying on their side, Champagne and other sparkling wines tend to age better if they are kept upright. This is because the internal pressure caused by the trapped carbonic gas provides enough humidity and protection from oxygen. The preference for upright storage of Champagne is shared by the Comité Interprofessionnel du Vin de Champagne (CIVC) who conducted an extensive study of Champagnes that were stored in various conditions and orientations. This study found that Champagne stored on its side aged more quickly because oxygen was allowed to seep in after the Champagne corks lost their elasticity due to contact with the moist wine.
I’ve also been advised to store my Port bottles upright (presumably not vintage Port though).
The Wiki article doesn’t have the entire story, but it’s point is correct. The only twist is that the advantage of storing upgright vs. sideways is almost insignificant and the space advantage 99% of folks probably have with traditional sideways storage outweighs any vertical advantages in my eyes. To me, the simple answer is that it is safe to store either way and I store 99% of my Chamapgne sideways (as do most in Champagne - even the people who did the study). In Champagne, the only upright storage you normally see is for old vintages in an oenotheque where space permits it.
Thanks Brad for confirmation. I’ve heard this before, and therefore mostly store Champagne standing up (but that’s REALLY because I’m out of rack space). A few that are still in 6-pack boxes are still horizontal. Sounds like I needn’t worry about either.