Mine did not start sleeping through the night until he was 2.5yrs. old!!!
there is a book called "The baby whisperer" it really helped my little one and myself when I thought I was going to go crazy w/ sleepless nights.
One thing I can tell you for sure, they say if the baby starts to cry; you either go in or you don't go in at all!! which ever you chose will be the one the child comes accustomed to. I know this sounds terrible; but I let my little one cry for 45min. when he was two and half, I never went in!!! He fell asleep and has every since.
Once I stopped giving in, he stopped trying to get me to give in. This may take a while and sometimes a month or so because they are so... used to you coming in, but if you stick w/ it, it will work.
and try the book. It is awesome
L