To be honest, I never thought about it yet. Though Hive account@jerrybanfield said that we need to have or invest at least $500 for our steem power. Lately, I've been doing power up 100% so I can increase my steem power faster but I had a discussion with a friend and we talk about how the earnings drop like crazy. Like in my friend's case the post earns $17 and on the 7th day my friend received only $9 from that same post. I may use default 50% 50% for my next posts and see what happens.