I think his 'time limit' is Obito initiating the Infinite Tsukiyomi himself. Both of them want to be 'the God' of that new world. So as long as Obito's busy toying around with Naruto, Sasuke, and the Hokage, he's got plenty of time. Also, it's likely that Madara's using this opportunity to observe Obito to understand his new abilities before he engages him himself.Lol Madara never seems to be in despair and besides 2 chapters ago he was a bit anxious about Obito's evolution and he implied that he had to use his trump card before the situation runs out of control. Yet he just went to fight Hashirama as if time wasn't an issue.