Powering down should be a sliding scale. You should choose the amount you want to power down, and that amount determines the time frame. So $10 would be an hour, or $100 a week, or $1000 a month, etc. That way, you can find liquidity in small amounts that you may need, but large amounts will take longer.
RE: My proposal: reduce the withdraw channel from 104 weeks to 104 days or even 104 hours to make steemit less like a ponzi scheme