It is your opinion and your choice, but you can not be sure that floods or earthquakes are not something which can not happen in your area. Maybe you can be sure if you do not have any big river near by, or you are far from the sea, but the earthquake is something that can not be predicted.
In case of hardware wallets most important thing is seed, the device itself can be stolen, but it is protected with PIN and it will wipe itself in case that wrong PIN is entered few times in the row.
We can read recently that one hardware wallet is survive fire and firefighters' intervention (lot of water), and one manufacturer is offering hardware wallet made from anodized aluminum.
You got it all right. I'm far from rivers and the seaside and there hasn't been an earthquake in my area like ever. I'm not in a tectonically active spot and there are no records of it ever happening here for the last 1000 years, so I feel like I'm pretty safe. Also, stainless steel containers are pretty solid, don't rust, don't burn and are airtight.
If the seed is the most important why would I use a hardware wallet for a long time storage. I will have to hold the seed somewhere anyway (like in that steel container in the garden), so I might do that anyway and save some money.
It survived but you can never be sure if yours will. Fires aren't the same each time and depend on many factors like the size of the room, the materials inside, amount of air coming in, and so on. The temperatures can be much different each time.
Sorry to say this but what if you die. what do you think will happen to your asset. your talk about natural disaster like flood and earthquakes but since you think that has never happened in your area you think flood cannot take place in the next 20 years. What if there is climatic change. Finally, I hope the container you intend to put your paper wallet is non-biodegradable because if it is your laminated paper wallet can become unreadable in the next 20 years. despite the hard scenario surrounding the storage of huge coin, I still believe the hardware wallet is the best option for now.
If I die my wife will know where to look for it. I know it will sound selfish, but when I die I won't really care about my asset. If a few Bitcoins disappear from circulation to be found 50 years later by some treasure hunter with a metal detector, they won't be missed.