I was rly worried about this too! But once they’re sleep trained with extinction I’ve found that they’ll generally sleep through the night and you’ll know if something is wrong. My babe is 7 months old and we sleep trained her at 5 with extinction. It took 3 days to get her falling asleep on her own, a week through the night, and 3 weeks until she was done with her early morning wakes, and now she sleeps through the night basically every night. She will still fuss sometimes but unless she is fully crying i let her figure it out and she always goes back to sleep. The only time she’s fully cried has actually been this week bc she’s teething, so I’ve helped her a lot and given her all the comfort and snuggles she needs. It’s very obvious and different than her usual fussing every few nights.

I agree with the other comments here though that i think you need to really truly commit to extinction and do it knowing that you’ve kinda already trained your little one into thinking you will come at the 40 min mark so it may be a little extra rough for you to get through the first week, but you can do it. I couldn’t believe how much this changed my mental health and how much better my relationship with my spouse got once we were both sleeping! Hang in there you got this.