I never left dd1 at all when she was a baby. I was a SAHM and I didn't even leave her with my husband so I could go out to the grocery store after she was asleep. I never, ever, left her. Looking back on it, it wasn't a healthy dynamic at all. I struggled very hard with the "balance" B of attachment parenting!
Now I have another daughter, and I have a new routine of going to the gym every week day. So I've been leaving her in gym daycare (it's the same lady every day, so she knows her and is really bonded with her) since she was 8 weeks old (and dd1 goes to daycare there too). Honestly, I love getting a little break from her every day. I love running while listening to my ipod, and then taking a shower all alone. Now that I get a daily break to do some self-care, I'm in a much healthier place, mentally, than I was when dd1 was a baby. We don't have any family nearby so this is the only way I can get time away from the kids.