It seems like forking so often would use up a system's resources very quickly. I'd imagine that each fork needs at least a handful of individual pages for OS bookkeeping overhead, so you'd get into the gigabyte range fast even with perfect copy-on-write.
Yes you can't run like that forever. But you could break, step forward and backward and bit, and then resume. I often step forward while debugging, realise that whatever is going wrong has already gone wrong, and would like to step back a few steps.
