As a carpet repair specialist with over 30 years experience I can tell you that dirt really is your carpet's worst enemy.
Sure you can vacuum your carpet in hopes of keeping the dirt out but how well does it really pull the dirt out of the carpet?
In my experience I've noticed that vacuums don't really work. sure they pick up the dirt you can see at the top of the carpet but they don't get deep down.
How do I know that the vacuums don't really work? When I sometimes fold the carpet back to work on the padding or the tack strip a cascade of dirt falls out of the carpet. When I pull out carpet I can see all the dirt that's worked it's way down to the padding.
Aside from staining your carpet dirt and sand have sharp edges that cut through the fibers of the carpet. Imagine millions upon millions of sharp edges cutting through the fibers.
A few common sense steps to making your carpet last:
Keep the dirt out of the house by placing quality wipe off mats inside and outside of each door. Sticky mats are best in my ever so expert and not so humble opinion.
No shoes allowed. Leave a shoe rack and a chair near your front and back door to make it easy to remove your shoes before entering. Then leave your house slippers inside where it's easy to just slip them on. Once you get used to having a no shoes policy in your home you will notice that it's very unusual to wear shoes in the house.
Vacuum well and vacuum often. I know I said that vacuums don't work but they do help a lot.
Get your carpet cleaned a couple of times per year by a professional with a steam cleaner.
Using rugs and runners help to avoid wearing traffic paths but they also are trip hazards and shouldn't be used at all in homes with the elderly. Also rugs and runners will prevent the carpet from fading with the rest of the carpet so when you want to move them, the carpet looks odd.
Clean spills right away. If you have stains you can find some good stain removal tips and tricks athttp://www.creativecarpetrepair.com/carpetstainremoval.php
If you follow these simple steps you will find that your carpet will stay clean and last a very long time.