He started writing his stories long before he was a Professor. It was while he was a young man fighting in the First World War.

Right, which works great if your daytime job is fighting in the trenches, but maybe less so if your only opportunity is software development or other mentally exhausting job.

Bravo lol

Personally I've found it much easier to sustain creative stuff on the side while doing a non-knowledge-based job than a knowledge-based one. Mental exhaustion is much more of a drag than physical. (Though the knowledge-based hours were longer too, which I'm sure was a factor.)