Maybe I missed something: Why encrypt the hard drive if I'm going to tape the password to it?
That was a brain fart on my part. Initially I had typed the part about having the drive and password in two separate locations, then thought "wait, it's a safety deposit box - they can be together" without taking the next obvious step.
The whole point of using a hardcopy is to avoid a number of problems with digital copies, the biggest of which is that harddisks, flash memory, and optical discs all suffer in terms of data longevity. They can also be damaged relatively easily, and, as someone mentioned above, data and hardware formats go obsolete and may be practically inaccessible in relatively short order.
At least some subset of this data won't be static - it'll have to be maintained. At least I hope he's not keeping the same passwords for decades! In that case it seemed silly to me to treat this as a separate problem from the fact (not mentioned by him) that people should keep a separate offsite backup of all their data. He should be doing that as well - so why not kill two birds with one stone?