How long should filament last in storage

Flagship K Series Creality Flagship K2 Plus & CFS
1

I’ve had an Ender 3 for some time, around 2005, and I bought a lot of filament. Three of them are still here. One each of Black, White and Wood PLA.

I’ve a new system and added the old filament to my available stock.. All were stored with silica and all show 10% on the humidity meter The Wood worked fine but the Black and White are very fragile. They break off in the Bowen tubes very easily. It isn’t much of a problem as I can keep reinserting it and it keeps restarting fine.

What is the expected lifespan of filament? Would it help if I left them out to actually get a bit more moisture in them until they get into the 20s at least? Any suggestions on the best way to use them.

2

Tough question, there are so many “it depends” and filament dryness is only one of them, Definitely, the dryer the filament, the longer it lasts. Additives to the filament can affect storage age too. Ironically it was your wood filament that lasted the longest.
Since you kept them dry all along, this probably isn’t the cause, but just for completeness; If PLA is left wet for too long the polymer can start to break down. re-drying it doesn’t fix it. You can still use it, but it will be weaker than fresh PLA.