Universal Display has quietly released a new PHOLED material performance chart. Their Green-Yellow material now has 1.4 million lifetime hours (LT50), and their Red color offers 900,000 hours. Blue is still very challenging, and their light blue offers only 20,000 hours (LT50).
20,000 hours to half brightness for the blue OLED phosphor might not be a problem at all, in the context of mobile phone displays. Consider that most mobile phone contracts are two years. If you had your OLED mobile phone on 24 hours a day the blue OLED phosphor would continue to be fairly bright for 833 days.