Yeah and this is the big problem that I have with the idea of passive income. Plenty of people talk about all these different things being passive income. But the reality is that the only way they are passive is by putting in hundreds of hours in the past.
The best way to turn any sort of passive income from older stories is to write stories that are evergreen. Topics that people always want the answer for. Also to write stories where you can reference a past story. So like if you are writing about SEO, see if you can link back to any previous stories about SEO as a natural part of the new story. I have found this is a good way to keep some of the older stories still getting some views.