I have to say that despite a good, solid routine, my dcs were all bad sleepers. Even now, I could expect to get up to one a couple of times a week.
In the early days it was all crap. Breast fed and co-slept, which probably never helped but how I did things. BUT, they do get better and it is not forever. The worst time was with dc3 and dc4. Dc3 probably struggled with the arrival of dc4 and needed one of us with her. We really were not prepared to get her to cry through it, just not our thing, but it caused awful nights.
All are good sleepers now at ages 8, 6, 5 and 3 however, nightmares happened. Kids wet bed occasionally. Winter saw some hacking cough that the kids seemed to suffer only at night. And dd4 is becoming dry at night, but I think this can wake them as they learn to get dry.
Just our experience, not what happens to everyone, but it doesn't last forever, fwiw, we would have managed much easier with three, it was the fourth that broke us!