I think this is a great idea, and I wish more people realized the value in things like this. I upvote all the real comments people leave for me and reply to them if warranted. It feels like the least I can do for someone who bothered to read what I wrote and internalize it enough to formulate a response.
Also, if you think keeping your voting power up is hard, try it without a slider! Luckily I don't get very many comments on my posts, so it doesn't deplete me too badly.
Yeah, I can't image how hard without a slider, when I was slider-less I just voted away and usually sat around 20-40% VP, It was a lost cause...lol.