Well, texture size does matter in a sense, because the amount of memory "reserved" with each render is larger, so you run out faster with progressive renders. However the point is that even with small textures - everyone will sooner-or-later hit the limit if the memory is not restored properly. And yes, sometimes even closing Poser does not release the memory, if you have gone past some unknown point-of-no-return and Poser has actually overwritten some of its own code in its quest for more memory, thus prohibiting a clean shut-down.