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      (let* ((msg (mailbox-receive! mbx-req terminate #f))
	     (last-activity (current-time))
	     (terminate (seconds->time (+ inactivity (time->seconds last-activity))))) ; the next message is due at this time, independent of how long we spend processing this message.
	(if msg ...
-----

-----
      (let ((msg (mailbox-receive! mbx-req terminate #f)))
        (let ((last-activity (current-time))
	      (terminate (seconds->time (+ inactivity (time->seconds last-activity))))) ; the next message is due at this time, independent of how long we spend processing this message.
	(if msg ...
-----