It's surprising how many people will throw out their old vacuum when it loses suction power. Chances are all it needs is a good cleaning, and this video shows you how to do it.
You'll need to clean more than just the bag! Vacuums actually lose suction power when filters or hoses get clogged up. It doesn't take long to clean it out, and get your vacuum back to running like new. Take care of even a cheap vacuum once in a while and it should last you a long time. Check out the video to see how it's done.
Cleaning Out a Vacuum Cleaner [Dan Jiles]