Just a quick question... when do babies' sleep cycles get longer? My understand is if they wake at 20' it's because they can't transition from light to deep sleep, 30' is because they are OT or UT depending on the situation, and 45' is one sleep cycle. When does the sleep cycle change from 45' to 90'? My LO used to nap 45' on the dot and is now doing 1 hour and 33 min on the dot. So I'm thinking he might have lengthened his sleep cycle? Or all my hard work paid off?