Julia,
Now I feel terrible for you. Sure, it's great to have the "luxury" of being there every minute for your puppy/dog. But if you're only gone two days a week, is that really cruel to leave a dog alone? I don't think so.
When my husband & I first were married, I wanted a dog so badly. I had not had one for the longest time in my life (3 years of dorm living). After an inspection that had taken much of our time to prepare for had been completed in Feb., I went searching. He disliked little 'yappy' dogs, but had actually listened to me when I had once said that I wanted a Yorkie when I was a little girl. He found the ad for 'Pepper' for me. She was 8 years old & a definite survivor who really needed out of the situation she was in. If we hadn't taken her, the owner was ready to have her pts because of health & problems with a young son.
Yes, we both worked 10-12 hour shifts. I worked 3 swings & 3 mid shifts with 2.5 days off. Michael worked straight swing shifts, 2pm- midnight. We also got called into work during certain situations.
We had a neighbor look in on her when we first got her. Pepper was usually sound asleep. When we came in, she'd wake up and come agrinning & asneezing at us. We took midnight walks during the summer & in the mornings before/ after work. She was a happy girl that liked her "alone-time." Similar to having a cat, except for being a dog. And yes, we gave her a loving home that she appreciated. Her life with us was much better than the one she had left. And while I felt bad that I couldn't be with her, she didn't seem to mind at all. (Today, thanks to Pepper, Michael loves & appreciates the small breeds)
Even now, with the two dogs, I can't be with them all of the time. They don't need it, either. My husband is gone until June sometime & I worked the last two weeks straight. I leave the rolladin (sp?) up about a foot, the door open with the curtain over it, & the girls go on the back patio to sun & take breaks. Sure, they're happy when I return, but they don't mind that I've left to earn their kibble :D The housemeister tells me that they've been excellent watch dogs for the three + years we've been here & no one has ever messed with them.
It just depends on the dog's personality & if it can handle being alone for a while. I do prefer a two-some, but only after the kinks of the first dog has been adjusted. Puppies have different needs, but many adult dogs are happy to just have a nice home & steady loving. I always believe that if something is meant to be, it will come along eventually & fit nicely into your life :D
good luck,
toodles