Most car ignitions will last at least 80,000 miles even under heavy abuse and neglect. Although you can make them last the life of the car by doing a couple of little things.
1. lubricate the keyhole with liquid lubricant such as wd-40 or graphite at least once a year. NOTE - If you live in a warm climate it is recommend that you use a liquid lube because using graphite in a warm humid climate, it turns into a thick mud that can cause the pins in the lock to stick. But if you live in a climate where the temperature can get into the negative numbers then you will fair better with graphite because wd-40 and other liquid lubes can get so thick as to cause the pins to stick inside the lock. Whenever using graphite always use very little because if you use too much it can clump in the lock and jam the pins and springs that are inside the lock. Using too much wd-40 won't cause any problems other than making a mess.
2. Don't let your key get worn out and keep using it. Here is how you avoid this problem. Make sure you have 1 new key and never use it. Keep it and make duplicates from it and use the duplicates until they get worn, then you still have the new key to get another duplicate made that is not worn.
NOTE - getting a duplicate does NOT make the key new again. New key means, new from the factory when you buy the car new or by getting a code key cut by a locksmith. The reason for this is because the action of inserting and removing the key from the lock causes the key to wear down over time, and getting a copy after extensive use will result in you getting a worn out copy. So I repeat again,
"NOTE" GETTING A DUPLICATE OR COPY OF A KEY DOES NOT MAKE IT A NEW KEY AGAIN!
Myth: Having multiple key chains will ruin your ignition.
Having a lot of key chains on your key will NOT ruin your ignition. Let me explain this, when you insert the key into the switch, you are supporting the weight of the keyring, once you turn the switch the lock casing, (which is thicker metal than a coat hook), is supporting the weight. Now there is a risk with having a lot of key rings on your key, the biggest one is the possibility of the weight causing a crack in the key that could cause it to break.
The act of using too much force or pressure while inserting or turning the key or using a worn out key is what ruins ignition switches. If you are jiggling the key to make it work, your key is most likely worn out. GET A NEW ONE! Before it ruins your switch.