How long can she go without eating?!

My daughter just turned a month old and I'm a FTM so sometimes I'm a little clueless. At this time she's usually eating 4 ounces every 3 1/2 to 4 hours. When I took her to her one month checkup the doctor asked me if she's able to sleep 4-6 hours during the night. Now I know she definitely can because I have the sleepiest baby in the world haha but I thought going 6 hours without eating was a little too long ? Should I allow her to sleep that long or should I still continue to wake her up every 4 hours ?