I don't know. I do know that a filament that prints well one day can print with a lot of steam bubbles a few days after, so less than 48 hours is my estimate. It will depend on the absolute humidity it is exposed to.

What most people do not realize is that relative humidity is a totally meaningless number unless it is given together with the temperature. The difference between absolute and relative humidity is explained here: http://info.zehnderamerica.com/blog/...the-difference

The equilibrium of water between air (gaseous state) and the polymer matrix (dissolved state) is governed by the concentration of water in the air (which is itself a function of temperature). Putting it simply, if the concentration is twice as high (expressed in g/m3, not %RH), then there are approximateley twice as many water molecules hitting the polymer surface per unit of time, and thus twice as many have a chance of entering the polymer matrix thus contributing to the water uptake.

So, given max abs. humidity at 15 C it might take a few days, given max abs. humidity at 35 C it might take mere hours.

If you live in a (sub-)tropical area, store your filament air-tight when not in use.

PS: In case you are wondering, I am a chemical engineer by profession