I bathed our babies every evening. It relaxed them for bed, and besides I like to shower every evening, too. Also, I figured they needed at least the diaper area bathed more than with a wipe. In the winter it was a quick bath, in the summer I let them splash a bit.
Every other day at first, about 6 months and later you can start once a day before bed to help them sleep. You could probly start the once a days at 4 months if you wanted but they don't get into anything to make them messy. Newborns glands have to adjust by themselves. If you over clean them they get confused. My BB had chapped skin on her forehead at 4 months, I was told her glands were just trying to figure it out. I put Vit E on them until they straightened themselves out.
After the umbilical cord stub falls off, I started doing it everyother day at first and now we do it every night, unless we were out. It's our daughters routine. Plus, she loves the bath! She has a ball splashing and soaking the kitchen!