User blog comment:FallenShadow/Fallen's Reviews: Chapter 341-343/@comment-7418318-20130711145215/@comment-7418318-20130711152855

That depends on the story.

While in the majority of stories they suck out a mans lifeforce the way you insinuate, there are also plenty of others.

Stories in which the Succubus sucks out lifeforce by just kissing or by entering the victims dreams.

In some stories the victim dies from this after a single time, in others their life is shortened and they only die from repeatedly getting attacked (though attack isn't always the right word) and in yet others the victims are just weakened but recover like it was just an illness.