Hi Sheena! Did you get snow last night, too?
Now to your question...I do what Rebecca talks about above. My calls are set up to go automatically to VM at all times except 3:30-5pm on workdays. That's when my kids are napping and I can take a call without having to ignore them. Once in a great while I make an exception and take an early-morning call before the kids get up, but those are always prescheduled and ONLY if it's an established client who I know isn't just being demanding as a power play. Otherwise, it's email or (if I'm in the middle of a billable project) IM.
I'm trying something new this year also: giving myself a 4-day workweek. It's kind of odd--no Thursdays--but it's that way because that's what works for my family. So far no one has had any problem with it.
I do the kind of projects that lend themselves to any-hours work, though. I can't imagine that restrictive a phone policy would work for someone who's doing a lot of real-time clerical work or things that require contact with the client's customers. You may just have to experiment until you find where your perfect balance is. My hours have changed at least four times since I opened 3.5 years ago.
And Holly--yep, I just rewrote my contract last week, and it's ALL in there now. I have a whole section detailing my hours, days, and communication preferences. Nothing wrong with being upfront about it. In fact, I think sometimes clients really appreciate when you lay your cards on the table from the get-go.