Bedtime

At what age has everyone started doing a bedtime routine?  My little boy is 5 weeks, and we currently just bathe him at some point in the evening when he is awake, then put him in his bassinet when we go to bed. I like the flexibility and the evening cuddles, but I do think we need to start a routine of bathing and putting him to bed at the same time every night at some point. Can I put it off for another few weeks or do most people start at 4-6 weeks?