I do also use this hippo I got from Wal-Mart every night and that helps him get back to sleep when he wakes up. It makes different noises and has lights that come out of the top. It turns back on by itself when he cries.
Every baby is different. my daughter has never truly got into naps, even at 1 month I was lucky to get 2 30 minute naps out of her during the day. the world is too exciting! we tried every sleep training method out there, and still at 5months she doesn't sleep through the night.
she uses a white noise machine now, so we are down to 1-2 wake ups a night which is wonderful compared to before. but day time is still happy play time, which I don't mind.
I do believe it works at any point. If I had waited six months my son never would have gone to sleep. I just did little things like during the day leave as much lights on as you can, and at night time as little lights as possible. My son takes naps lots of places but he always sleeps in his crib at night. If I put him in there any other time he will scream but at night I tell him Its night night time and kiss him and he goes right to sleep. He sleeps from around 7PM until 7AM. Since he was about 2/3 months old. It took some serious work to make sure you do the same exact things every night (obiously unless they are sick or something) but it really is possible.
You gotta sleep train, but the earlier the better. I don't believe the books saying u can't until they are 6 months. My daughter goes to bed at 830, Wakes at 5 for a bottle then right back to sleep until 8am. I started sleep training program at 3 weeks. It was hard but it only took about 2 weeks to get her there.