Long term storage of Onyx outside of the Dry Box will severely degrade the print quality produced by a spool. The plastic filament readily absorbs water from the atmosphere. This increased moisture content will degrade print performance, and may clog the print head. If you need to remove the plastic from the provided Dry Box, please store it in another air-tight case. Markforged recommends the Pelican 1430 case as the gold standard.
If you are planning on leaving your printer / material unused for an extended period of time, just keep the spool in the Dry Box with the filament loaded in the printer. The Dry Box & desiccant do a good job protecting from moisture, and Dry Box-stored material should last up to a year before the water content is too high for printing. When re-starting a machine after a long idle period, run the Wet Plastic Purge utility until it stops steaming (which may take 2-3 runs).
Store all composite filaments at room temperature in a cool, dry place, out of direct sunlight. Kevlar® should be stored in a bag or container which blocks exposure to all light.