he's the kind of guy who doesn't want to get caught, everybody is watching those blocks, if spent, his identity will be revealed in no time. He probably bought coins in 15,000 chunks on the early days and living on that instead.
a solvable problem: he could just split up his wallet and send his private key to a random person over the internet. as in he'll pay a bounty or transfer it to someone else for whatever reason. better yet, he might donate those coins for charities to circulate them instead of leaving them to rot.
if i were satoshi, and i knew that people were closely watching my wallet/blocks, i'd just donate the money.
