How does a revshare affiliate program work for long-term earnings?

I’ve been looking into revshare affiliate programs because I’m aiming for sustainable passive income over the next few years, but I’m still unclear on the nuts and bolts - how exactly do they calculate and pay out commissions on an ongoing basis, what happens if subscribers churn or become less active, and are there any real-world examples of affiliates who’ve built six-figure earnings purely from lifetime revshare without constant new referrals?