I recall Patrick Faure saying towards the end of last season that he could have asked the engine guys to give him 20bhp more, and he was entirely convinced they could have done so, but the risk/reward balance did not favour it at that stage of the season.
IMO Renault played it absolutely correctly last season - fast out of the box, consolidated mid-season and played it safe until the very end where they could show off and take their chance on reliability for Shanghai (esp as the engine was only going to do one race).
Whereas the Maccas were forced into taking risks and luck was not on their side and whatever the rights and wrongs of Rons comments about his drivers JPM (again IMO) threw away several points by poor strategic driving.