I had a 12L bottle of 2001 Cos d’Estournel that was stored on its side that was leaking pretty badly. I was pretty concerned for a while. When we finally popped the bottle, the wine was absolutely flawless though.
Similar experience with a 6L of Chapoutier Hermitage.
I’m guessing due to a relatively smaller surface area that could be potentially oxidized inside the neck it doesn’t seem to effect larger bottles as much.
Also, due to 3L and up being hand cut corks, they tend to leak more in general. Had a wine distributor tell me they see it all the time with larger formats.
No 3Ls in the cellar yet, but I will buy some eventually. Going to have to figure out a storage plan for them, definitely on their side. I have a fairly good start collecting various magnums and those are all on their sides.
For my 40th a couple years ago I opened 3l bottles of ‘78 Mondavi Reserve and ‘78 Leoville las Cases that Had been stored on the side for 40yrs. Personally I would rather store on the side and see leaking if there is a problem with the cork, which would make me pop the bottle sooner than later. If you store upright and there is a faulty cork you would never know until the wine is oxidized.
When I was in my first post-college apartment, my girlfriend (now wife) and I thought that Meridian California Chardonnay was the bees knees. One day, while out on a sales call, I had some time between meetings. I wandered into an Albertson’s somewhere way out in Port Orchard, WA. Of course, I wandered through the wine aisle. There, up high on top of the shelf, was a 3L bottle of Meridian Chardonnay. I asked if it was for sale and it was. We threw a pretty great fish taco and Chardonnay party with that! There’s something about large formats that make any event special, even if the wine is the likes of Meridian!