How many years do you have to FIRE?
My personal decision matrix would look something like:
1-5 years: nopety nope
6-9 years: maybe
10+ years: go for it!
As your own boss, you could probably set certain boundaries to preserve work/life balance. If it really is a situation involving a ton of OT no matter what, then your time to FIRE becomes a big consideration. That is, how are you managing work-life balance over your lifetime? Is it a front loading plan? If you'll spend 4-5 years working your ass off 70h/week to build a business only to walk away when you're done in year 5, I'd skip the hassle. If, on the other hand, you've got a long row to hoe, then I'd say go for it. The maybe range reflects a tough call factoring in kids/relationships, risk, best alternatives, hatred of existing job, etc.