Trivially: fire you, and hire another poor shmuck at your starting salary to spend 90 hour weeks in time for the next launch.

If they are willing to do that once, rewriting everything using a coding pack animal, it is pathological and they WILL be willing to do it twice, regardless of whatever reassurances to the contrary they give you on a death march.

The 40 hour workweek as a standard isn't arbitrary, it's about preventing workers from creating a race to the bottom on hours worked, because that ends with anyone unwilling to be driven like a slave becoming unemployed.

Do your part and defend your right to your personal time and to go home unmolested after your workday ends.