Good friendships last forever... As long you eject people from your life when they need your help. Think about that for a moment, and what it should mean if your good friends are as incredibly self-centered ad you are.
Be wary of friendships which are one sided. If a person doesn't value their own person and they constantly need you to help them that's not friendship it's dependency. I've never ejected people out of my life the first time they needed help, but I have given up on people when I realized I was wasting my time. Many people who need help can only change with their own effort.
Every relationship is one of opportunity. Think about that!