So long, farewell, good riddance. These are our parting words to the Cost Per Install (CPI) Index as, this month, we announce we have officially retired it. Why? Well, although it still has a role, CPI should no longer be the central metric to measure app marketing success. We don’t think advertisers should focus on it — so we’re not going to focus on it either. Marketers and advertisers are now dealing with a heavily saturated app market and realizing the lifetime value of a user is more important than just high app install volumes. They understand that using more…..