Listen to Stef here.
Basically, if you are building an engine like this, you just don't want to green very early at all - it is much better to overbuild first, because A) it makes you more consistent AND B) it lets you go bigger when you do green, which compensates for the time lost. So greening early is one of the biggest mistakes I see people make, probably because they feel they are behind.
Of course, you need to green eventually. Usually this is either to get yourself on the favorable side of three-pile endings, or because if you green now, and your opponent either follows or builds a little more, or even a lot more, before greening, they can't possibly catch up - you have enough firepower to just blitz through most of the VP quickly. Here, with the SR giving lots of potential total VP out there, this means you should be able to get all the provinces in like 3 turns when you turn to green, or you are reacting to your opponent, or there is a 3-pile threat. Of course, the biggest thing is that you need to follow the actual game - these are only rules of thumb, and in a specific situation, they might be broken.