Doesn't hurt. I'm running two of those services, Lifelock and Identity Guard. Identity Guard informed me one of my passwords was on The Dark Web. Got nary a peep from Lifelock. It was an old password, but still...
I have Experian IdentityWorks that was free from one of the breaches.
Best things to do is use system generated passwords that are different for each site and use password manager to access these sites. For you super sensitive shit (email, banking, lemonparty.org, etc.) use a different password manager or just remember the passwords.
I would not pay for it, but should not hurt except for sucking your cash.