I was sitting here today as I opened up a bottle of "natural" 7-Up. Does the carbonation last longer if the soda is cold? Or if it stays out of the fridge after opening? For some reason my father in-law or the rest of the family never puts 2-Liter Bottles in the fridge after they open it. They always pour it from the bottle and put ice in it. Drives me nuts! Anway, does it last longer in or outside of the fridge? Just a curiosity question.

If I remember my 8th grade science correctly, gaseous activity increases when a substance is warm. Therefore I'd definitely recommend keeping the 2Ls in the fridge after opening. Also the cap doesen't seal as well after you've opened the bottle, so if it's warm, it'll go flat faster.

yeah I agree. I usually put 2 liters in the fridge after i open them when i have enough room for them. They taste a lot worse if you leave them out on the countertop and pour it in a glass with ice. That waters it down, so if its in the fridge its already cold and tastes better.