There is a four-five year study at UC Davis (and I think other funded research in Europe) that examined the question of oxygen and closures quite closely. If someone can get a copy of that, it would be great. It was finished in December 2011.
Apparently all corks and other closures (incl screwtop) do breathe a tiny bit. Corks have a wide range of breathing (oxygen transfer rates). I think the study found that there was also wide range of oxygen getting into the wine on the same bottling line! Also the study found a wide range of oxygen getting into the aging from the air at the head of the bottle when corked (I'm presuming due to variability in the cc's of air at bottling). The oxygen transfer rate of the cork is only the third and one small little component. Nomacorc funded this research and said "hey, we can make a cork with any oxygen transfer rate you want, but what is ideal?" Too inert and you run reduction risk. Too much oxygen transfer rate and you run oxidation risk. The result is that Nomacorc is out with a line of artificial corks that have a selectible oxygen transfer rate (Nomacorc Select Series; Select 700, Select 500, Select 300, and Select 100). The Select 100 is for all practical purposes, inert -- like sealing with wax I would guess.
I'm not too clear on what the reduction risk is if you have a completely inert seal, but I sure know what the oxidation risk is, so I'd be inclined to go toward an inert seal. If you really want oxygen in a long long term aging bottle, why not just open and reseal it or let in a little air every five years?
I'm inclined to try and make an inert seal. You get a lot of aging from the O2 which is in the wine and the O2 which is in the head air -- my guess is that that might take you through many years of aging with a big red before it stops aging without any oxygen transfer through the closure.
If someone can explain reduction risk, I'd be very interested.
AJ