Nad
Here are some signs of needing to transition:
1. Not taking as much at a feed (baby not as hungry at 3 hours)
2. Erratic Night Wakings
3. They are extending their awake times
4. Starts taking 45 minute naps
A window opens up during the babies 4 month, that means they can stay awake longer ('A' time) and go longer between feeds. Keep a diary of when they eat and how much, how much activity they have and how long they sleep for.
If they don't eat very much on the 3 hour mark and take shorter naps this is the time to transition.
The fourth month window sometime coincides with a growth spurt, but unlike earlier growth spurts this one not only involves giving more food during the day but also extending the 'A' time between feeds. If you don't adjust his/her routine then this is the month when sleep problems start appearing.
Most four month old babies can stay awake for up to two hours during his fourth month, but if your baby can only stay awake for 1hr 30mins to 1hr 45mins, then you will have to transition him/her to a 3.5hr EASY, until he/she can stay awake for closer to 2hrs.
If you are on a 3.5hr EASY then 'E' will be 7, 10.30, 2, 5.30 and then top up at 7.
Then you can transition baby's onto a 4hr EASY.
https://babywhispererforums.com/index.php?topic=63161.0 - routines
HTH's