Using Vue 7 Complete on a Vista 64bit system (3.16GHz Core 2 Duo with 4GB of memory), my scene has 7 standard terrains with ecosystems on each plus a global painted ecosystem. The scene also contains 50 or 60 plants and trees that are not part of the ecosystems. After several hours of trying different atmospheres and lighting setups, all without closing the program, my resources are still above 75%. Saving and loading scenes usually takes less than 5 seconds.