As others have said, there is no OSFA answer.
For me, family time wins and if I had my time over again I would have FIREd prekids. I've been on a slow downshifting journey for nigh on 2 decades...but only learnt about FIRE a couple of years ago. I would have liked to be a SAHM, but my now ex did not agree, so I worked part-time. Then became a single parent for last 14 years - and stayed part-time. My hours have gone up and down ( mainly between 0.5- 0.7 FTEs) and changed shape according to my children's ages/ needs/ locations. So at one stage I worked evenings, since that was what childcare I could get. At one stage I swapped houses 1 night a week with my mum since I worked a fair way away, but closer to her house. For a long time now I've worked shorter days to be home in the afternoons after school.
A couple of years ago when I found ERE and MMM, I was working 0.7 and very burned out and my workplace was increasingly treating me like a full timer. Was excited to make a plan to retire earlier at age 60 instead of 67 or so. After nearly a year of MMMing, I decided to work only 0.5, which would shake up my duties at work so I couldn't be treated like a full timer, help me recover a bit, and be a bit more available to the teenagers. To do this though, I blew out my FIRE date to 62.5. Its all worked out splendidly, and living on less (I had to shed 28% of my budget) has been no problem. The hardest part has been the slowing of the NW increase. Its worth it, but I do still feel it.
Interestingly, though, with ongoing improvements in my MMMing abilities, I've gradually made ground and reduced that time to 61.5 years. Recently a few more mustachianly practices have taken root and I've hatched a bold new plan to retire at 60 again. Its a stretch goal but should be doable.
Our tax rates here are high: if I worked full-time, a lot of the extra would be lost as the tax rate for that proportion would be mostly 45% ie I would take home just over half. I had thought about just biting the bullet and getting it done, but it becomes inefficient because of this. A lot more pain, teenagers unsupervised, and essentially being paid a lower hourly rate. For me, not worth it!