It depends if you write for work or pleasure! :)

Actually doesn't depend much. For pleasure some twenty years ago I wrote some code. Then five years ago (15 years after the original authorship) I wanted to make some changes.

Now most peoples' long term memory isn't that good; mine is no exception. It was a struggle to get the appropriate platform running (eight inch floppy drives, etc.)

However because I didn't neglect documentation and comments, the actual revisions were a pleasure, as was the original design.