I've only recently gotten to page one on Google for many of my keywords, but since i've been there (about 3 months) I've stayed rock solid, or gotten closer to number one. I update my site several times per week, and users post comments all the time (more content!), so the site stays pretty fresh.. My question for those that have been at this longer than I've been, once you start getting good rankings, is it safe to assume that you'll be there for a while?
Yes.The only concern about this one is if your competitor outrank you because he doubled his effort to get you out of that SERP.So keep on updating your site and get as many as possible quality backlinks.