Thanks so much for the advice. It's very helpful to know that other people have been there.
I should have mentioned it, but we do walk her in the morning before we leave. We get up at 5:30, mess around with her for a while, take her for a walk from 6:00-6:30 (not actually 30 minutes of walking, but with her a 15 minute walk takes 30 minutes most of the time), feed her, mess around with her some more, then off to work. It's hard to know how much she sleeps while we're gone. She DOES sleep in the "open space" on weekends when we're home, but definitely not for 9 hours a day. I keep reading about tethering her and I know we should try it, but at 17 weeks she's 40 pounds of constant nipping, biting and jumping, so I can't wrap my mind around how it will work. I guess I should just try it and see. I really wish we had done it when she was younger, like so many other things.