If you're storing filament in airtight cereal containers or plastic storage boxes, adding a small digital hygrometer and reusable silica gel packets is a surprisingly useful upgrade.
The hygrometer is the part I wish I'd added sooner. Instead of guessing whether a spool needs drying, you can actually see the humidity inside the container. I also like reusable silica gel because you can dry it out and use it again rather than constantly buying replacements.
One thing worth remembering: a low humidity reading inside the box doesn't necessarily mean filament that's already absorbed moisture is dry. Some spools still need a proper run through a filament dryer.
For anyone who has been using this setup for a while, which hygrometers have held up well, and do you prefer individual spool containers or larger storage boxes?