Well, I'm pretty sure its shorter then 104 weeks, due to the increasing steem power every week. I get every week an increase of at least 5% in Steem Power. But only 1% is powered down to steem. So next week i get more steem during the power down, because I have more Steem Power. And the week after even more. Etc etc.
Or do you think it doesn't work like this? BTW... I totally agree with your advise! Only put small amounts in Steem. And only money you don't need in the future.