My DD started staying at my parents' house for few day stretches when she was about 7 months old because I had no care over Christmas when the creche shut and I had to work. They live a couple of hours away so she had to do overnighters.
She still goes and stays with them over the hols. She loves it!! So do they!!!

I actually thinks it's important for a child to spend overnight time from their parents. It helps build independence and confidence (IMO).