Weirdly, my sleep is way better with kids than without. I was always staying up too late (grad school), but now it's impossible -- I have to be in bed by 12. Their sleep schedule regulates mine. YMMV

Legit commentary, however, point 1, the phase of lowest sleep is temporary, and point 2, with kid #2 and I presume onwards, you've been through it before and it's easier to adapt.