What age to start a sleep routine?

[Stillmonday]

My baby is 4 months old and we practise safe co sleeping. I've started taking him to bed about 8.30 and feed for a while then he will fall asleep around 9.30/10pm ish.
I know he should be going to sleep earlier but is there any point introducing a sleep routine now or waiting until he's a little older?

I haven't read the full thread because I expected there's a lot of talk of "rod for your own back" and such.

When did I start a nighttime routine with DS: when we came home from hospital.

When did he comply with the nighttime routine and actually start to sleep: age 2 (years!)