I have about 2-3 gallons of an old ale in a corny I need to transfer to free up the keg. I've been aging this beer for the last year, drinking a pint every now and then. I thought about filling 2L PET bottles, keeping one with a carbonator cap on it, the rest fitted with screw caps (with CO2 in head space). The one with the carb cap I would serve from, and as they empty one by one, I would carbonate with the cap. Question is, how long can you keep beer in these? Are there issues with oxygen permeation through the PET? It might be another year before they are all consumed.