Activity time for a 10 week old is 1.5 hours total, from the time they wake up (this includes eating). With the 1.5 hours of sleep, that equals a 3-hour EASY. At around 4 months old, the baby can slowly be transitioned to 4-hour EASY. To extend the wake time, try keeping the baby awake for an additional 15 minutes (past the time you notice the sleepy cues) every few days.
If, however, your baby starts getting sleepy before that amount of "A" time is up (in your case, he/she is getting sleepy just 45-60 min after waking up), then by all means let the baby sleep. It's more important to go by the baby's cues than forcing that timeframe on him/her. Try extending the awake time after a week or so.
(Moderators, please correct me if I'm wrong as I'm a little rusty on the infant EASY... I'm just getting back into it.
