Summer humidity averages 15%RH and winter humidity about 40-60%RH outside. Generally my indoor humidity runs between 30-40% @72F but I don’t do anything special to control it.

I store almost all my PLA and ABS in open racks and rarely have a quality issue (Bambu, Kingroon, and Sunlu brands). My engineering filaments (PC, PET, ASA, and especially TPU) I will dry before use in an AMS-HT and keep stored in sealed containers with dessicant just as a housekeeping necessity. Sometimes I leave them out and it’s fine, but they are $ enough that I take care of them to avoid scrapped prints.

If you can’t get RH lower than 35% after 48 hours you need to renew or exchange your dessicant. Drying works by heating air until it’s RH is extremely low which causes water to migrate out of the plastic into the air via vapor partial pressure, then it gets absorbed by the dessicant to be removed from the system. OR, some dryboxes (ams-ht) continuously exchange air from the outside, which is energy intensive but provides a continuous supply of hot, dry air to remove water from the system.

Dessicant can only achieve an RH equal to its own saturation, which increases with exposure time, so starting with very dry dessicant is a necessity.

Air exchange is less effective in very humid climates, since your heated RH% will be higher, so sealed drybox + dessicant is usually preferred there.

If you aren’t actually removing the water with dessicant or air exchange, it will just stay in your drybox and return to the same RH you started at once it cools down.