"Optimizing Your Mac -Performance and battery life may be impacted until completed." I have already finished the installation. What is left to complete?

Adding on to a very old thread usually means just one thing: you are spamming/advertising a product which, in this case, is not only completely unnecessary, but can also wreak havoc on your Mac.

I just finished an update and have the message "optimizing your Mac".... After reading all the threads I'm not sure if I should not do anything until the message disappears, or if there is something I need to do since I have this message. Do I just wait until this optimizing finishes?

Never mind.... I did nothing and the box in the right-hand corner has gone away, so I assume whatever optimizing was being done has completed. I also now see this thread was not about the OS X Yosemite that I'm using. If there is a way to delete replies I would have deleted my prior reply, but I don't know of a way to delete.

That message, I believe, is the system working/installing the update. Also give Spotlight some time to finish its' re-indexing.

As for deleting posts: you cannot - you can edit your post for 15 minutes and replace it with a period (.) or 'deleted' or some such, but that's it. However, it is best to start your own thread with any issue - in this case, it was in the wrong OS version forum, which doesn't help you and the discussion was more than a year old.