What is the average life expectancy for an African Dwarf frog?

I had this question once also and as I was reading over the net I came across a story about a woman who had hers for 25 years and the thing was still alive! She was saying how everytime she would go on vacation she'd expect it to die in the petsitters care but it never did. I've had my frog for about 2 years now. Who knows, maybe my kids will inherit her!