From #21140, msg215485, Raymond Hettinger: "Students commonly save shell sessions as a record of everything they tried in call. It would nice if there were a way to trigger a periodic autosave (perhaps every five minutes or so)."

For Shell, autoappend would do the same, and saving on each >>> rather than by time might be more appropriate.

On idledev, Jeff Silverman requested autosave, I presume for editor windows.  If one is doing closely interactive development, hitting F5 to save and run every few minutes, this would not be necessary.  But if not, ... I know that autosaves in other programs (editors and games) have saved me lots of trouble more than once.

Saving every n minutes should be trivial using .after.  With slightly more work, it could be every n minute the window is active (has the focus).  Any untimed save should reset the timer.  Since IDLE looks at every keystroke (I believe), counting keystrokes and saving every n keystrokes might be possible.

I list below other IDLE issues containing 'autosave', so I don't have to look at each issue for relevance to this one again.

#21140  22 Idle: saving an OutputWindow should default to .txt (patch)
           (Has comment prompting this issue.  Otherwise not relevant.)
#23666  10 Add shell session logging option to IDLE
           (Related to this issue, partial duplicate)
#21937   6 IDLE interactive window doesn't display unsaved indicator
           (Actually, *...* indicates non-empty undo buffer.)
#19042   9 Idle: add option to autosave 'Untitled' edit window
           (On F5, same as for titled edit window. See 1326830.)
#4765   20 IDLE fails to "Delete Custom Key Set" properly (patch)
           ('autosave' in quoted .idlerc/config-main.cfg)
<closed>
#1175686 79 add "reload" function to IDLE
            (Closed as dup, 'autosave' is about F5.  Not relevant.)
#1326830 125 python scratchpad (IDLE)
             (Rejected.  19042 is a re-opening of this.)