It's a bit more complicated than that; there's a common-law concept, usually called the rule against perpetuities, to prevent exactly that sort of permanent interest-gathering account. There are ways to try to get around that rule, such as setting up a very specialized trust; but even making the attempt requires a bit more than just opening a bank account.

That said, if a cryonicist is up to making the effort, it's at least potentially worth the effort.