Twice today I lost a fair amount of work on a web page because my login timed out while I was editing the document. The second time I think that I had been editing it for less than an hour. Does anybody know the timeout period? I didn't save more frequently because the document closes when it is saved (and opening it again is a bit annoying, but not nearly as annoying as losing all of my work when I click the Save button).

Hoping somebody can tell me more about this annoying timeout feature,