Depends on the rainbow table. There are some out there that are a couple of gigs in size, with precomputed hashes for everything from A to AAAAAAAAAAAAAAAAAAAA
On average how fast can they blaze through one of those really huge lists to crack a very random passphrase ?
I guess if you have something you really need to keep secure use pencil and paper and keep it under lock and key.
I keep my 2 feet on the ground, and my head in the twilight zone.