Does not using your immune system make you live longer?

I know it's a "pathetic" question. But don't take it lightly yet. Why do you think a dog only lives 10-15 years? Why do Africans only live 40 years old on average? Cavemen only lived for like 30 years. It's probably because they work the crap out of their immune system and then their body gets all tired. In fact why do you think animals live way shorter than humans. Same reason probably. I don't use my immune system at all considering this. I am the immune system kind of. I wash my hands a lot, etc. But then again, I take vitamins to strengthen my immune system just in case I catch something. What do you think of my theory? I really want to know because I'd rather not wear out my immune system and die quickly.