My son is 17 months and doesn't sleep through the night either. He has a few times, and I was shocked when it did happen. I kept waking up during the times when he usually starts squirming, but he was sound asleep.
Anyway, I'm kind of glad to hear he's not the only one. I haven't tried much to "fix" it because it doesn't bother me too much. A typical night for us goes like this: he falls asleep at 9pm, wakes at 10pm to pee, goes back to sleep, wakes at 1 or 2 to pee and/or nurse, goes back to sleep, wakes at 5 or 6 to pee, goes back to sleep, wakes at 7 or 8 at which time I potty him, and try to nurse him again to go back to sleep, (once in a blue moon it does and I get to sleep in) but usually end up getting up for the day.
I guess I always figured that if he didn't wake up to go potty that he would probably STTN, even though I know other EC'd babies can go all night with out having to potty.
Maybe it's partly that he nurses so much still to fall asleep initially, and then again during the night. One thing I have noticed that does help is a good bedtime snack (almost a meal sometimes). If he gets filled up on cottage cheese (his favorite) then he stays full longer, doesn't nurse as much, and sleeps in longer streches, though not really "through the night."
Another thing that wakes him and/or keeps him from falling asleep is that I think he get the "jimmy legs" as we call it (aka RLS). Some nights he just cannot stop moving his legs! And when he does fall asleep, he'll wake up 30 minutes later because his legs start twitching again.
On these nights, I try some infant massage techinques on his legs and feet. It seems to work ok.