If you're looking for an appropriate timeframe, you have to put his whole career in games in context. The first game he's credited for is Wurm Online, which he worked on between 2003 and 2007. He was also employed by King at least through 2009, when he started on Minecraft.
That is 6 years. Minecraft has been around for 5 years. If we take the premise that Notch comes up with really good ideas once every 6 years he works on games, he'll hit this timeframe next year.
Alternately, the clock might only start from the moment he stopped personally working on Minecraft, which was in November 2011. In that case we will have to wait another 3 years for him to collect ideas.
That is 6 years. Minecraft has been around for 5 years. If we take the premise that Notch comes up with really good ideas once every 6 years he works on games, he'll hit this timeframe next year.
Alternately, the clock might only start from the moment he stopped personally working on Minecraft, which was in November 2011. In that case we will have to wait another 3 years for him to collect ideas.