You’ll find a lot of opinions on this—a lot of them just wrong.
Link to a thread from a year ago: What do you find best suits your filament storage needs?
Based on that very long thread I got a lot of great information, here’s a summary of what I’ve learned about moisture and storage from the ideas presented in that thread and my own “verified” experimentation. Read between the lines: Verify whatever is said here, just don’t take my word or the word of anyone else!!!
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What may look watertight is not necessarily so. Given enough time, plastic containers will allow water to migrate inside, even those with a tight rubber seal.
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Desiccants don’t dry filaments; they dry air. The dry air helps prevent latent moisture from re-entering already dried spools. Read between the lines here: If you put a wet spool into a sealed enclosure with desiccant, you end up with wet desiccant and drier air—but not necessarily drier filament. I suppose that, given a few years in a dry-air environment, an argument could be made that it would dry the spool. But absent that amount of time, you need to heat the spool to force the internal moisture to escape. That’s what spool dryers are for.
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Sucking all the air out really helps deform your spool—if that’s what you’re going for.
Most of us would consider that bad. 
But you already knew that. The only purpose of over-vacuuming a bag is to visually confirm negative air pressure, assuring the seal is intact. Beyond that, it serves no purpose. -
Many people swear by exotic forms of dehydration storage—like $100 sieves for a single spool. Not exactly economical.
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Did you know that a cheap $0.40 moisture indicator card can tell you at a glance how much humidity the storage vessel absorbed over time? A cheap hygrometer will tell you how much moisture is in the bag at that moment, but it won’t tell you how much was absorbed over time. Also, those cheap indicator cards can be dried and reused multiple times.
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My experiments have shown that a reusable storage bag with desiccant and a moisture indicator card works just as well whether I vacuum seal it or not. Try it for yourself: set up one vacuum-sealed bag and another that’s just ziplocked, then leave them in a corner for a couple of months. Compare the indicator cards. You’ll find no significant difference.
Recommendations based on practical experience:
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Don’t over-vacuum – Over time, you’ll ruin the shape of the spool. It doesn’t provide any real advantage. The difference in air volume between a tight bag and a looser one is negligible in terms of absolute humidity. A decent 50g desiccant bag is more than enough to keep things dry inside. This is especially true for partially used spools, where less filament means less structural reinforcement.
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Instead, vacuum just enough to visually confirm negative pressure.
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Food vacuum sealers may feel reassuring, but they’re not better than reusable bags. They’re just a pain in the ass when you need to reseal. A quick-store, resealable bag ensures you’re more likely to actually put the spool away—even if you forget to vacuum seal it. If I had to rely on a heat-sealing food vacuum, I’d be far less likely to do it in real time and would probably forget altogether.
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Comparison shop “Filament” bags versus food storage bags. Often a search on Amazon and you will find the exact same bag under food storage for about 25%-50% less. Imagine my chagrin when I found identical bags but better sized in the food storage section of Amazon for 50% less.
Also, I found that many of the filament bags were oversized whereas you can get smaller right-sized food bags that fit a 1Kg spool perfectly. But note, prices change frequently.
https://www.amazon.com/s?k=moisture+indicator+card
https://www.amazon.com/s?k=vacuum+food+storage+bags+resealable
https://www.amazon.com/s?k=printer+filament+storage+bags+resealable