One thing a lot of people have missed that deserves to be noted -- powerdown is not really 104 weeks.

If you have, say 50000 steempower, and you start a powerdown today, you'll get your 50,000 steem in something like 8-12 months. As inflation slows down, it will take closer to 14-18 months.

I've fiddled with the math, and it looks to me like if you take the %yield on steem, and figure out how long a 200% increase would take, thats how long it would take you to power down your full amount of liquid steem. After that, the rest would be interest income