Don't know the answer to this one, but would like to!
It wouldn't matter for Rodinal (the stuff lasts so long you eventually find it's up and moved to Eastborne (okay, Florida for our colonial bretheren!)) but DDX on the other hand...
Assuming it doesn't oxidise while frozen and any separation can be cured with a quick stir (two assumptions which may not be valid)...
I've just had a vision of little pots of frozen DDX waiting until my next processing run of Delta 400, and no more expensive dev getting slung out 'cos I don't use a litre within n months! Hmmm....
Thoughts anyone?