I read somewhere that you want to try to keep it up above 80% then allow it to regenerate and then continue upvoting. Doing this would be better than voting down to 50% power then waiting. Basically while you are at a higher %, the regeneration time is also faster allowing you to hit 100% faster. I'll post again if I can find it.
Found it, its called intermittent voting. A graph is shown highlighting the differences of voting to 0% vs voting to 80%. Please refer to this:
https://steemit.com/help/@r4fken/steemit-basics-how-long-does-it-take-for-voting-power-to-reach-100-again