Probably, you won't do a "Save" after each and every compile or upload.
Unfortunately, we found that if you send too much of the Arduino's output to the serial terminal the terminal window does not accept any more strings and - which is much worse - the IDE does not accept any command such as the "Save" command.
So, if you run an application which is sending text to your computer over a long time make sure the source is properly saved.
Otherwise you might have to use the task manager ...
Time line of releases