Yes you should certainly upvote your own content. That is one of the major benefits to being a large holder of Steem Power. What you say matters more than someone who is less invested in the platform. Effectively, large holders earn higher content rewards and require less curation than smaller holders.
The only reason to not upvote your own post is if you don't care about the rewards or the added visibility. Perhaps you think the rewards are better distributed among others. Perhaps it is a low value post.
It isn't even possible to prevent someone from doing it, so we should consider it to be part of the rules of the game. Upvote your own post if you think it is worth an upvote from others.
RE: Should I upvote my own content?