I know that nursing duration varies from baby to baby, but I would like to know at what age your baby became "more efficient"?

My little girl used to nurse for 45 minutes to an hour, within the last month or so she whittled it down to about 30 minutes. Now all of a sudden it's lucky if we make it to 30 minutes and it's usually closer to 21-25 minutes, sometimes as short as 17 or 18 minutes. She's still getting the right number of poopy and wets and gaining weight well, so I'm not worried she's not getting enough. She was sick last week and staged a nursing strike during (I was lucky to get her to nurse 10 minutes over the course of a 30 minute session with her screaming and fighting the whole time, sometimes she'd only go 2 or 3 minutes before positively breaking down), so my question is more about whether or not this is her new normal or residual from her being sick.

She is 4 months old and will be 5 months in about a week and a half. When did your baby become more efficient and start nursing for shorter periods of time (regardless of how long they were originally or how short they became)? Did it happen gradually or overnight? What has been your experience?

*****I know they say "watch your baby, not the clock" and I do. The only reason I pay attention to times is to know what her normal is and recognize if there is a shift in her patterns, not to obsess over making her nurse for x amount of time and/or freak out if she doesn't. I guess I'm just wondering if this is her new normal or if she'll go back to 30 minute sessions.

Sorry if this makes no sense, my head is pounding 🙃