When you kick a girl out (or leave her place yourself), you set excellent precedent – for the long-term of that relationship.
There's one very special thing you should do with every girlfriend you plan to be with longer than a month or two.
It's a thing she will always remember - one of those memories that sticks in the brain.
She may not necessarily cherish it... but then again, she may.
That thing is to kick her out.
You can also leave. Though leaving is less powerful than giving a girl the boot.
You don't want to do this capriciously. You should only do this if a girl truly gives you a good reason to.
Fortunately, women being the boundary-testers they are, sooner or later every girl will give you a good reason.
And when you give her the boot - or take your stuff and go - you set a precedent for the entire rest of the relationship that makes everything else you do easier... because it's backed up with teeth.