A lot of banks have been phasing this product out, but if your bank supports it, I highly recommend it. Usually, they’ll even allow you access with a drilling fee if you’ve lost the key but can show multiple forms of ID. Whether this is good or bad depends on your threat model.
Either on your keyring or in your fire safe. As I mentioned, if you lose it, you can get the lock drilled at the bank with sufficient ID. All trust waterfalls to meatspace trust providers, just like if you lose your Yubikey AWS support will reset your hardware 2FA with sufficient evidence you are you.
Just a note about safes... our community had a wildfire sweep through, and I have not heard of any fireproof safes actually working. Some were cracked open, or were so compromised they could be snapped apart by hand; some survived, but there were only ashes and melted metal at the bottom. I'm sure I didn't hear about the successes, only the failures, but still...
I don't want people to proceed with the notion that those safes are actually fire-proof. Consider them 'fire-resistant' safes that conditionally offer some extra protection.
Every single one of them probably "worked" as designed and marketed, or close enough. Safes don't claim to be fireproof and will clearly state something like "Fire protection for 1/2 hour at 1400F." Very few get into "Likely to survive the total burn-down of a home" territory.
Fire address AFAIAA are rated by time normally, so they'll be rated to withstand a fire for an hour - giving time for the fire services to extinguish it. A safe that survives a whole house burning to the ground seems like almost an impossibility.
