How long do you have filament sitting “in the open”? I mostly print with a single filament roll at a time, and just leave it on the printer. A 1kg roll lasts me several weeks. For long time storage I keep it in an air tight box with disiccant pouches.
But how long can I let it sit before I should start storing it with disiccant and/or drying the filament before use?
How long depends on your humidity. If you live somewhere with high humidity, PLA or PETG filament can go bad in a couple of weeks or less. In a dry location, maybe never for PLA. Nylon will go bad anywhere in a matter of hours. It’s not easy to tell if filament is wet - weighing filament can tell you about the moisture gain/loss, but of course doesn’t work when you are actively consuming it. When filament gets wet, prints start to get bad in various vague ways that can seem like printer tuning issues. Sometimes it’s bad bed adhesion, sometimes poor first layer quality, stringing, or bad overall print quality.
If you want a good storage solution you need an airtight box. I use Iris Weathertight storage boxes with 1lb desiccant canisters and a humidity monitor. The 62qt box can fit 16 spools and room for the desiccant.
