There was a post the other day by asking why we shouldn't all just always power down. He argued that it was essentially costless since you still get "interest" while powering down, and I responded that it's not entirely true.
There is some cost to always power down: In the time after your VESTS have been converted into Steem, and the time you choose to power it up again if you choose to take that option, the price of VESTS per Steem will have increased at least a little. Thus you will be taking a small opportunity cost every week. The larger cost though is that you're creating for yourself a time and cognitive overhead, every week you must remember and set aside time to make a decision about what to do with your (highly inflationary) Liquid Steem. So if you choose to always Power Down, Steem Power is no longer a 'fire and forget' investment, no longer a purely passive income which you can check up on every few months, as just another part of your long term investment portfolio.
Despite that though, "Always Power Down" is probably a good option for many users here. The flexibility benefits as argued by are pretty huge. Right now on Bittrex SBD are trading at the equivalent of $0.83. Buying SBD at a price like that and converting it to Steem is a gamble, but it's one with about a 20% edge. The result of many plays should be a lot of profit. The opportunity and flexibility to enforce the peg and make more money doing so, or to divest from Steem if necessary, should be more than worth the cost for those who are already quite engaged with the Steem platform.