For those who go to an office everyday it's easy to know when quitting time is. Most people leave most of their work at the office and go home around the same time everyday. Even if they do bring work home, it often doesn't have the same sort of urgency as it would at the office.
We mom bloggers are always within a few feet of our office. It's so easy to check an email real quick. But rarely is it quick. We get sucked in to the screen and next thing we know the kids are going to bed and we missed out on spending time with the family.
Why are you working from home? Chances are it has at least a little bit to do with spending time with your loved ones. You aren't doing that if you are working 16 hours a day. If possible, place your work station in a room with a door. Determine your working hours and shut that office door when they are done with. Get out and live a little. I like to schedule the bulk of my working hours early in the morning, because I am a morning person but no one else in my family is. I'm done with most of it by lunchtime each day. I have an hour built into the evening where I can catch up on anything else I need to, but I try to make sure I have nothing to catch up on since its so easy for an hour to turn into three.
The important thing is to get a life. Step away from the computer each day. If you don't you will get burned out and you'll get even less done. You may also miss your children growing up. It really does happen that fast.