A reliable friend is someone you can count on, and won't stand you up. They are willing to share good and bad times with you. Caring friends value each others feelings as much as their own. They accept their friends weaknesses as well as their strengths. If you judge people, you have no time to love them.
Some friendships last a lifetime, but many fall apart.
But friendships also grow apart. People's interests change as they get older, and they might want to find friends who have more in common with them now. Don't walk in front of me, I may not follow. Don't walk behind me, I may not lead. Walk beside me and be my friend.