Step 1: Get out your wallet and prepare to pay an obscene markup for calibrated sand that the vendor got for a tiny fraction of the price he's charging you, from a secret supplier he'll never disclose.
You have to replace (or even touch) them literally NEVER, if you have another easily-refillable source of humidity in the same container (e.g. a gel jar chargd with PG, or similar). It emits humidity and the Bovedas do "2-way buffering" to smooth it out. You get rock-solid RH, zero hassles, and can refill with distilled in seconds, although with plastic/Tupperware it's necessary only very rarely. As I said, the Bovedas never have to be replaced or even touched.
If you don't even want to pay the markup on the ready-made PG gel jars, you can just make your own with the generic super-absorbent polymer, any plastic jar, and some 50/50 PG solution, all of which are dirt cheap from lots of well-known suppliers, not super-duper-secret suppliers like the bead re-sellers apparently use (and guard the identity of closely).
Lots of guys here look down on the PG-infused gel jars, but if you team 'em up with Bovedas, it's a hell of a great, cheap, low-hassle solution. Yes, yes, everyone says they have a mold problem, but 10 years later I'm still waiting for it, and it hasn't happened yet!
Pudding Mittens wrote: