It wasn't a reflex nor have I done that often, but I was certainly tempted to save whenever I heard Bloodsuckers in STALKER. If I saw one before I could hear it then it was usually too late to save, and I had to get rid of the thing. In the vanilla game it's not much of a problem (the first playthrough, however, was another story) since they're pretty much all scripted and spawn at the same places. But with mods that tweak the spawn points and allow them to roam more freely, and during night time, yeah then it's very tempting.