Today I revisited some code I'd written about a month ago and reduced the time it takes to run a data loading job from 52 minutes down to sub-10 minutes by replacing a relatively slow API call with a direct call to local code. This is something that was "good enough" until now, but was on my radar as being eligible for improvement. Since I had a new data loading job that would take over 10 hours using the API call, I had to write the new job a better way. Copying this better code back where it could make a difference meant that all of my data loading jobs were now refactored and much faster.
The takeaway here for developers is to periodically revisit your code and refactor it. Find new efficiencies. Examine how your code has been working and consider what you might have learned since the last time you worked on it. You may notice something now that you didn't notice the last time you were in the code.
A small amount of time doing this can pay off in huge improvements.