I read an interesting article saying that day sleeps impact night sleeps in a big way. Apparently having less day-time sleep doesn't make for a better night-sleep. My DS (only 5 months) was having zero daytime sleeps, until I started to force it. I have to sit with him and hold him while he naps, or he wakes straight up. (probably not practical for you with a NB) It sucks, but it's the lesser of two evils. If i can get him to have at least 2 naps during the day, he's better at nighttime and less likely to become overtired.

If there's any way you could coax him into a daytime nap.......... go for it.

I'm not sure exactly how many hours of daytime and nighttime sleep a 20 month old requires, can someone help me with that one?