I save literally after 2-3 mins at latest, basically i start wondering when i last time saved and save again. I save a lot.
That comes through learning. I've had cases where hammer loads blank file if i tell it to load the map vmf again after crash when it asks. So i say no and open it myself. I've also had hammer loading broken file, because hammer was saving at the time as my pc crashed or power went down. So literally it screwed up the file itself by autosaving. Autosaving also causes random lag on bigger files, so i have always that turned off.
I suggest everyone to keep 1-2 day old backup from your file in different location or drive. That way you don't lose anything if the bad things happen.