In my opinion this is situational question and powering up comes under situational category. And when we want to study the situation, most of the times there is no perfect definition for it because it's an Individual perspective what is the best time. There are many cases like below which is included in situational category.

(1) Investor who is long Term Hodlers.

(2) Coin collector who just want to expand Steem Power.

(3) Want to invest but don't have money.

(4) Don't have money to invest but putting efforts in Engagement and converting rewards into Steem Power.

(5) Don't have enough money to invest, but investing time and efforts, in return getting effective rewards and want to invest liquid rewards as Steem Power but withdrawing liquid rewards to go through from the expenses.

So, in my opinion all these are situational scenarios.