"Ray Andraka" wrote

Why, what does that do for you? Air is 78% N2, and 21% O2. The O2 is a
bigger molecule than N2, so I wouldn't expect to see any difference in the
leak down. The only benefit I am aware of relates to tire fires in
airplanes that go much higher and faster than our spam cans.

It would be an interesting science fair project for a suitably inclined
middle school student though!

It is an increasingly common practice, and it does seem to leak more slowly.
Heat transfer is also helped.
It is even becoming more common with tire shops for cars.
--
Jim in NC