How to earn more from selling your Vote on SmartSteem

When I first started to sell my vote on Smartsteem, I said why not spend my whole voting power on it and earn some of that SBD and STEEM. It surely doesn't go like that.
For example if you set it to use 80% of your voting power, Smartsteem will upvote people for you as soon as you get 20% Steempower, and you will definitely earn less, but if you leave it to upvote people at 95% of your voting power, you will earn more SBD and STEEM, plus you have enough steem power to upvote other good contents or as you wish to spend it.