starting as old as 7 wks old, a baby can sleep up to 12 hours at night and still be fine as long as during the day they are getting the proper amount of nursings/bottles and wet/dirty diapers.
Optimal sleep per 24 hours period is 12 hours at night plus 3 two hour naps for a total sleep of 18 hours, until at least a 8 mos old, then they may drop the last nap down to an hour or out for a total of 16 to 17 hours until at least 17 mos old, then it can drop down to 15 hours until at least 3 yrs old. YEP, that is what I said, fifteen hours every 24 hours until 3 yrs old. Then it may drop down to 14 hours around 4 yrs old, but never below 12 hours until at least 7 yrs old.