I love in Colorado, which is a pretty dry state, so while I had heard of "wet filament", I never considered it to be a problem that I would have to worry about. I had seen people creating dry storage bins for their filament, but figured that must just be for people in humid climates.
When I first bought my 3D printer a few years ago, I did what most people probably do - I bought a 10 pack of different filament colors. Everything printed great for a while, but eventually, my prints just started to kind of suck. I made a few upgrades to my printer, but still couldn't pinpoint what was going on. What was frustrating, is that some times my prints would be great - but other times I couldn't even print the most simple prints without problems.
I eventually noticed that my great prints were from newer filament that I had recently purchased, but my bad prints were coming from spools I've had sitting out for a while. So I purchased a $40 filament dryer on Amazon and it instantly fixed all the problems I'd been having.
I feel dumb, because I had gone through three different extruders, new hot ends, new nozzles, tubing, and spent tons of time cleaning and tightening stuff on my printer. I had left my printer untouched for months because it was just so frustrating. Something as simple as old filament left out never occurred to me until much later.
TLDR; If your prints have started to suck after a while, you might want to try drying your filament.
Quick addendum: Cheap digital hygrometers from Amazon can be off by as much as 10% or more and are kinda pointless, poorly designed and a waste of batteries.
Simply using some color changing desiccant will save you a few bucks. (It's something I use here in Colorado for my jars of.. "entertainment products".. that is legal here, in addition to my filaments.)
There is desiccant available that is formulated to hold specific humidity levels but filament is better served by pure silica gel.