Breastfeeding is different. First of all, night feeds help maintain supply. Another consideration is that night feeds help delay periods returning (though that's more a benefit for mum LOL.) Night waking is also normal and biologically adaptive.
But at 4 weeks the worry is that a baby can be sleepy and not feed when they ought to. Also if a baby is in their own cot they may wake but go back to sleep without waking you, especially if they have a dummy. Personally I wouldn't be happy letting a baby under 12 weeks old go more than 5 or 6 hours overnight. After about 12 weeks as long as they are getting plenty of feeds during the day and weight gain is good then I wouldn't wake them, but before then I would.