John Carmack on mutable variables

This would require coming up with an order of magnitude more variable names which is just unnecessary cognitive load.

An order of magnitude? That sounds like pretty outrageous hyperbole. A variable getting reassigned 10 times sounds extremely rare, the average in my experience has to be less than 1 reassignment. I think the approach requires coming up with maybe 10% more names.

Usually there are good, obvious names for intermediate calculations in my experience.

I'm open though - what kinds of things are you doing that require reassigning variables so much?