Curation rewards encourage to vote for same persons

Not really. Curation rewards favor voting on the same things that other people are going to vote on. Later voters do not get significant curation rewards by piling on, though some do continue to do so anyway in the mistaken believe that they will.

If I vote on @dollarvigilante again after voting for him the first time and it turns out he doesn't get votes any more because others have lost interest, then my vote does not do well. Simply voting for the same people again and again does not generate good curation rewards unless those people remain popular and continue to get votes from others.

If later voters are voting for stuff they don't like, they are the ones screwing it up and responsible for not getting the content they want, not the whales or bots who vote early. The latter are responding to the incentives set by the former.

In short, unless you are a power curator (whale/bot), just vote for what you like. The power curators and profit motive will respond by giving you what you want.