DS is 8.5 months but really didn't enjoy baths at all until he could sit up in them properly, he hated lying back in them. He has a bath most nights now but we only did one every 2-3 days while he disliked them so much. Of course we top and tailed carefully if he wasn't having a proper bath. I think if they haven't got especially grubby, or hot and sweaty, and they're not yet crawling around, they really don't need one every day.