I worked on an assembler/editor that had a change-to-run system on the order of a couple of seconds, too.

Something changes when you have near instant turnaround time. It's magic.

Some of the most miserable time I've spent has on projects with tooling where builds took hours, and often hours just to fail. I was even okay with 30 minute turnaround time, as long as it was clear that the bottleneck wasn't fucking lame tools: The need to burn a bunch of EPROMs for each build, for instance . . . though I fixed that as soon as I could.