I know from Tracy's book at around 4 months of age most lo's go to a 4 hour EASY for example (not all but most). Below is an example of a 4 hour EASY.
E 7am wake and eat
A Play time
S 9-11am nap
E 11am wake and eat
A Play Time
S 1-3 nap
E 3pm wake and feed
A Play time
S 5-5:30 CAT NAP
A Play, Bath, PJ's
E Bedtime bottle
S 7pm bedtime
If your lo is not ready to go 4 hours, then maybe start with 3 hours and then move him up from there. It is really good, like Monika stated, to have your lo on a predictable routine to create order. Babies thrive on routine, which is very different from a schedule (following only the clock instead of following your babies cues as well which is key to EASY - following cue that's is).
Melissa