Baby is gaining but wants to sleep alot

Soo the doctors all say wake and feed every 2-3 hours while newborn but our newborn just started sleeping almost thru the night. She’s gaining weight and almost back to her birth weight but for example she slept 11:30-3am then 3:40 to 9am and we had to wake her! I know she sometimes lays in her crib for a while before she fully falls asleep so the exact time before she fully falls asleep might be off a little but is this healthy.