P.P.
I have a 3 and 1 year old and at that age and even now they are on the 7:30 or 8pm thru 6am wake times. My kids woke up during the night once maybe twice until they were around a year. They'd tend to wake like this while I was still nuring them, sick, or if they were cutting teeth. I'd say about 10 hours and if the child wakes you can either ignore or check to see what the issue is. Maybe it's just the teeth.