Toby goes down between 6 and 7pm. He is usually wanting a feed around that time so he has the feed and I put him down. He sleeps straight through till about midnight/1am and then will wake again to feed at about 3 and 6am.
My DD goes to bed at 7 and has been since she was about Toby's age so I'm keen to get him moving towards that so they are both going down at the same time.
I don't think you can start trying to establish bed time too early, it might take them god knows how long to "get it" (up to the individual baby) but it certainly doesn't hurt to have the routine happening.