Or you could just put a majority of your coins onto couple of cheap thumbdrives, encrypt them, and put one in a safety deposit box and another in a bubble wrap envelope with your last will and testament.
But that's still putting all this money into a single basket, bitcoins. It does not matter if it's stored in different wallets, it's the same currency. If the exchange rate collapses or something happens to the currency, you have 25,000 BTC valued at $0.
I invest all of the $ salary that I don't spend, I invest into other areas half of the $ earnings I get from trading, it's a common sense security against something going wrong. Even if you lose all your earnings or they got stolen, you still have whatever you invested into these other areas, which with time represents the majority of your capital.