Why does the 'edit' button disappear on a question?

You know when you post a question, and there is an edit button on it after you posted it, why does it dissappear? Thanks, because I was to edit one of my question titles because it isn't getting any answers.

Thanks

There is a small window of opportunity for editing questions, after that, the edit function disables.

You can ask an advisor to edit your title for you.

You'e an advisor =]
Please can you change the title of my question 'What are some good free mmorpgs?'
To 'What are some good games like runescape?'
Pleease =]

Thanks

Yay... thanks =]