Whether you're living together or not, quality time in a relationship is important. You should be able to hang out at any time of the day or night, and plan spontaneous outings without it being a huge deal. Otherwise what's the point of having a partner? Of course people have their own lives, but you've got to make room for that special someone in your life.
Maybe she's refusing to see you when you've both got a weekend free. Maybe you spend your Netflix nights alone these days, waiting for her to walk through the door. Maybe you can't even really reach her on the phone anymore. There'll be excuses and vague promises, but the writing's already on the wall - she'd rather spend her time with another hunk.