I have stored unused Kodak RA-4 and C-41 developers more than three years without degradation using the storage method I described earlier. Others on this site have posted similar experiences. Despite this, there continue to be those here who think color developers have short lives and in some cases deters them from doing color processing. I guess Kodak's literature is a big part of the problem. Perhaps there should be a sticky thread on this subject.
The Mason jar idea sounds a lot better than soda bottles, both in terms of air tightness and not being an eyesore.