Most people don't bother to keep their resume up to date. They wait until they have serious problems or dissatisfaction with their current job, and then at the last minute they slap something together. Updating your resume should be a constant process - even when you are happy with your current job, you need to be working on it.

Why should you keep working on your resume? For starters, it's easier that way if something comes up. You don't have to sit down and think about all the things you've been doing over the last ten years. Also, even if you're happy with your current job, you should think of your resume as a way to advance your goals within your job. You should always be thinking about what you want your resume to look like, not just what it does look like. Figure out where you want your job to go in the next five years, and take on new duties at work that you think will make your resume stand out for that direction. You need to decide in advance what you're going to want to do. If you want to stay with the company, what position would you like to have in five years? If not, what job do you really want someplace else? After you've answered that question, figure out what an ideal resume would look like for that job. You should go online and search around - try to look at people's resumes who are searching for similar jobs. Then, try to add to your resume to make it fit within that field. You can do this at work or outside of it - learn a new skill that is useful for that job, or volunteer outside of work for something related to the skill. Volunteering is the easiest way to get experience in an unrelated field - people will readily take you, and you can do something good at the same time that you're helping yourself.