Can I Bring My Plants Inside On Cold Nights?

Hey this is my first time posting on here and also my first near-successful grow and my question is that up here in Maine we are starting to get nights dropping into the low 40's which I understand can really stunt plant growth. Is it okay to bring my plants inside on nights that get that cold or does constantly bringing them inside every other night hurt them in anyway? Thanks in advance.

Bring em on in... No problem...
Make sure they continue to get 14 or more hours or the plant will go into flowering...
Cover at night if left outside if it gets too big to move... and you're right temps below 50 or more will stunt the heck out of it.