Re: Saving Draft feature - session lifetime
It's probably stating the obvious but there is an "Edit idle timeout:" setting in the Wiki admin area - its about a third of the way down the Wiki features list - but it looks like the maximum setting is 30 mins. I've always assumed this does indeed change the idle time you have but I've never tested it.
I've never tried the Save Draft feature since it seems to need the experimental Ajax features which may or may not be particularly stable.