It's not clear to me when worksheets are saved in a persistant state (in a file).
I've lost changes I've made to worksheets many times after "save and quit"-ing and then having either the VMware, notebook or windows crashes, not shutdown properly. The only way to restore data is to cross your fingers and hope that snapshots have been made (when are those made? can their creation be triggered manually?).
What's the proper way of shutting down notebook so that this issue can be avoided?