When is lipstick too old? Is there any other uses for it, I have so many its a lot of money to through out, can it hurt lips, cauce infections etc?

According to this article, the shelf life is 1-4 years depending on who's giving the opinion:
http://beauty.about.com/od/makeuptri.../shelflife.htm

It notes "What everyone agrees on is that if it smells rancid, throw it out, it's spoiled. It can cause fever blisters"

Delilah, it's good to replace your lipstick every year as bacteria can collect and live on the stick. A change in the way it tastes or smells means to toss it out!