I feel I should mention that I printed about 4kg worth of filament that a buddy had stored in his garage in a rubbermaid tub for six years. I think it was all PLA. This is in maritime Washington State, no climate control, stuff wasn't even in ziplocs. As a consequence I'm skeptical that moisture matters as much as has been implied.
I do keep my filament in vacuum-evacuated ziplocks with a little desipack but that's the extent of my prevention.
I think that formulation can be shit, and what people think is "moisture" is actually 'shit formulation' because they don't print enough. I, on the other hand, would buy 3 1kg rolls in the same lot, print one in two days, and then the second one would be garbage while the third one would be fine. Talkin' less than a week.