When I first started this job, there were no job descriptions. I created a standard template for analysis and description based on some that I had found online. It is not quite a fill-in-the-blank, but is a good standard template for how our company operates. I have used some of the descriptions on places like salary.com, other job posting sites, etc. There are a couple of good job description websites out there. I have also found if you search google with "title job description", I usually can get a jump start.
My responsibility is putting together a basic description and then handing it off to the manager/person in the position to edit. I have never presented them in a formal setting beyond giving them to candidates when they interview.
I find that I make changes when we decide to post for a new job opening and/or an employee's job duties change. I would say about every 2 years I would change any one description. I do have some descriptions that I have created that have never been used.