5 or 6 days. It wasn't quite the same thing though. I was very ill with "morning sickness" with baby #2, and we had to let grandparents take our son (age 2) to their house for about a week. They lived 3 1/2 hours away from us.
It was a blessing they could do it.
As far as "fun" trips? Mostly just one night... at the most 2. But, we had a pair of little ones by then (ages 4 and 1) and we'd go to my parents' house (6 hours away), and stay the night, then husband and I would go on to another town and spent a night or two, then come back and spend another day or 2 with my parents with the kids.
Leaving them home alone with husband would have been fine. It is harder when it isn't you OR your spouse there. But then, my mom was fantastic with the kiddos when they were little. We were VERY VERY comfortable with that arrangement. But, never more than 2 nights even then.
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It will be good for your daughter and your husband for you to do this for yourself. They will make memories. And bond. And yes, Daddy will not do everything exactly like you would, but you know what? They will both survive and it will be just fine.
Go. Enjoy.