no need to worry because google is not going to penalize you to edit previously publish post. I've known some pages that have been edited several times for months and years but those pages are still in google page one until now, even after getting edited for quite often.

No problem, unless you go nuts and optimize that thing like a lunatic!

In fact, people should edit/add stuff to their old posts everynow and then

It is perfectly normal to edit your posts every so often and I have not noticed it affecting anything negatively. I don't do it that often but I do have to make changes sometimes and it's fine.

I have tweaked my posts and never had any problems, but I certainly do not do it every day, just occasionally.

Doing minor page edits isn't a big deal SEO wise, the things you defiantly should never do once a page is ranking is, never edit the URL (unless you know what your doing with a 301 redirect), be very careful about doing major <title> edits.

If the page isn't ranking yet, you can do all the edits you want, again, be careful with URLs If you have already built backlinks.

Simple little URL edits can kill a ranked page in the SERPs.

Example, these are not the same URLs, they look similar, but the difference can drop a ranked page in the SERPs very fast (notice the URLs vs ):

) http://www.warriorforum.com/adsense-...d-wp-posts.htm

) http://www.warriorforum.com/adsense-...-wp-posts.html