Well, the last voting session lasted 20 minutes because a lot of people wanted to use @tipU service at the same time and the amount of available votes was quickly used - I have little control over this :) With STEEM price going up and more delegations it should be better.

you refund part of the bid because you cannot upvote with your announced 200% return.

The main reason for refund is that @tipu will spend more voting power on new and interesting posts.

What would be your "perfect point of performance", I mean delegated SP, vs. sustainable vote?

Can you rephrase the question please?