I noticed that sleep needs changes for my LO around 18 months so I had to do some tweaking and found it helped to cut his nap down a bit. Prior to 18 months, this was our routine:
a: 8am
s: 1-3pm
s: 8pm
At 20 months, our routine is like this:
a: 7am
s: 1-2:30/2:45
s: 8pm
DS seemed to need more A time in the morning and less nighttime sleep. This change finally took care of our NWs.
HTH!!