Waking a sleeping baby for feedings

I've always been told, "don't poke the bear." But then your read all this stuff about needing to wake your baby for feedings every so many hours and other things about issues if a baby isn't eating so much so mamy hours. It's confusing.. my LO is a week old today and she's a heavy sleeper. EBF and she will sleep about 3-4 hours if I just let her be, but everything I read says to wake her every 2-3 hours. And at times I do try, sometimes shes easy to stir by just picking her up or changing her diaper. Theb other times, there is absolutely no way of waking her.. my question is, is it an actual problem for concern? My first born was nothing like her. She's just mellow and content where my boy was up on the dot for every feeding sometimes sooner.