I usually save about every 30 minutes, more when I'm building. I also go into Manage Worlds, and that tends to save it really well, then I go back in. In the past I've had many times it didn't save & sometimes it's because it's buffering & only way to get out of that is to Control, Alt, Delete. Sometimes that happens when trying to download something from the gallery & it just won't download, once again it just buffers, & I have to Control, Alt, Delete. Which can also mean you lose what you were working on. So going into manage worlds & saving on the regular, helps.
