I do that, too. I will make one tree become maybe five, by rotating and doing slight angle and size changes on the duplicates. I've never used such a quantity, though. It must be a hunger for as much realism as possible. Possibly hidden under that canopy are millions of tiny, digital caterpillers munching on the leaves. There are nematodes in the soil and cicadas humming from trunks and branches. They cannot be seen, but they are probably down there, working to add realism to the scene. Off the subject, but I once did an image of a man on a islet with about four palm trees. It was a simple image, but I wrote that just off to the right, just out of sight, I had a four-masted schooner, highly detailed, with a crew of thirty-five different characters. It slowed down the render, I said, but I put it all there so the man you COULD see would be looking at it in a realistic way. I sometimes forget my Poser characters aren't living actors.