My lo sometimes does this too, she always has and I have tried everything to wake her and she just wouldn't, so I decided to leave her be, because it was just too frustrating to try to wake her and even when I did, she couldn't stay awake, so we would and sometimes still do, go 4 hours between feeds. She normally wakes fairly easily if she's gotten 3/3.5 hours of sleep and then I feed her, but then she's gone 4 hours between feeds, however, it's always worked out and she's been fine. She's gaining tons of weight, and still gets cluster fed normally for me it's 5/7/9 or 4/6/8 and I don't do a dreamfeed and she still sleeps 7-8 hours at a stretch at night. So, see what works for you-hope this helps!