Most Spiders have a lifespan of up to 2 years.
The average spider lives to about 2 years although some spiders can live a bit longer than that.
However some spiders have been known to live up to 20 years when in captivity as pets.
The female spider also lives a bit longer than the male spider and male spiders reach their maturity within two years and die after mating.
So the spiders you see that are not in captivity will not live very long even if you don't kill them or they don't get killed some other way.
Spiders can be very beneficial to your home and yard as they can help eat other bugs that are more of a pest than a spider.
Although some spiders are poisonous and those poisonous spiders should be killed to prevent them from biting someone in your home.