I've found I have to exit P6 regularly, and even then, I need to make incremental backups under different filenames. Sometimes I have no textures applied and haven't even rendered once since starting Poser, and the memory bug nukes my files. Usually when I'm running hair or cloth sims.

But I still like P6, and consider it money well spent. Assuming they fix this bug, of course, which I'm confident they will.