The humidity where I live averages 65%. I pre-dry every spool in my Creality dryer before placing in AMS. I may only open the AMS cover once every 2 weeks, for just long enough to change a spool. If I add a bunch of the printed desicant containers, How long can I expect my AMS to stay below 20% humidity?
It’s good you pre-dry before putting spools in the AMS because the AMS really only dries the air to help keep filament dry. To dry filament properly takes heat.
But it’s still basically impossible to answer your question because we don’t know how dry you keep your AMS and how dry you get your filament.
Filament has desiccant behaviors. If you get your filament dry enough, you will see it lower the humidity in your AMS.
As to filling up your AMS with silica gel, that also depends. If you keep the silica gel “dry” then it will scavenge water out of the air and keep your filament dryer for longer. Don’t keep your silica gel dry and it eventually becomes a water source and gives up the water it scavenged from the air to presumably drier filament.
Silica gel is deceiving. If you don’t have indicator to know about where it is water-wise, it can get loaded up with water and be a trap waiting for dried filament to wet again. You always need to keep any desiccant in the AMS “drier” than the filament or else it can give up water to the filament.
Best way to answer your question is just to run with it and see. I thoroughly dry my filament and the desiccant packs I last changed out last month in my AMS units had been in there since early last fall. I couldn’t keep the AMS humidity at 1 any more even with fresh dried spools. Over a month now on the new desiccant and still reading 1 on both. Should hopefully stay that way until about May.
But much depends on how you do things, what the actual humidities are, how dry you get your filament, etc.