I personally up vote the heck out of just about everything. I think there should be silver and gold badges for up voting. It would obviously be easier to up vote your way to badges but I think something hard like 1000 up votes for a silver and 5000 up votes for a gold could be helpful.
Heck even giving gold badges for every 5k or 10k votes might be something to think about. The number is large enough that even someone dedicated to using all 30 up votes a day would only get 1-2 badges a year (max votes per year is 10,950 and 10,980 in a leap year).
If you look at Stack Overflow as an example there are not many people who have broken the 1000 or the 5000 up vote marks. I honestly can say that the lack of up votes on Stack Overflow has slowed the pace at which I hunt for questions to answer. If I see something and I know the answer I will surely answer it but I don't hunt stuff out as much.
This site does seem to be a bit better at voting but I do see a lack of votes from people over 1000 Rep in general. Reaching out to the top performers could help but that would only make a difference for a while. Until there are more or other motivations to up vote I think we will not see as many up votes.
The issue is to make sure that people don't get over rewarded for up votes and create rep inflation which will make rep less valuable. It is a very tough balancing act.