Ordinary posts give out quickly, I use mine up too fast I'll admit. I think those ones that "boost" (and I've seen that happen with me) is when you happen to hit a trending post.
I'd be lying if I said I understood it completely. I've been thinking of not doing as much upvoting to let my voter battery "recharge" but hey, I like doing voting and comments! Is that a crime? :)
I know!! It's so hard not to upvote. I feel guilty, like I like your post but I'm being stingy about it, when I'm really just outta steem.
How do you know when you're out of steem?
Go to steemnow.com and enter your name on the left sorta middle of the form
I'm glad this is a topic because I did notice the value of my up vote would be high on the first one and low on all others. I experienced a jump in a trending post yesterday too. Now that I know its the norm I can chill out.