LTV, lifetime value, measures how much a buyer is worth by adding everything up: the initial purchase, the upsells, the recurring billing renewals, and the purchases that follow.
It's the number that decides how much you can afford to pay for a customer. An operation that only looks at the first sale has a low ceiling for traffic investment. One that knows its own LTV can afford to pay more for acquisition and still stay profitable.
Approval and chargeback feed directly into this math: a customer who can't pay the renewal, or who disputes a charge, cuts the LTV short.