I'd imagine this would vary considerable with the type of tea.
Just one recommendation, I think, if you're concerned with achieving optimal health, it's best to not think too much about EGCG or any other one chemical in tea, and instead think about tea as a whole ingredient.
The trend I've seen in recent years from researching health and nutrition is that focusing on specific chemical components nearly always leads to poor health decisions, with respect to food/drink and diet. The reason for this is that chemicals interact with each other in complex ways, and any one chemical is both good and bad, but usually has the best effects on the body when consumed (1) in moderation and (2) in combination with the other chemicals with which it is naturally (and traditionally) consumed.
So, while I'm sure you could probably answer questions about ECGC concentration and infusion number...I'm not sure how useful this answer would be. In the end, I still recommend people to stop thinking about ECGC and other antioxidants and instead focus on the quality of their tea!