This is a thought I had mostly to do with Lemmy but I feel likes it’s relevant elsewhere in Fediverse.
As far as I know Lemmy doesn’t lock posts after a set amount of time like Reddit does and I feel like this is a good thing for smaller niche communities. For example if I created one for a one off video game or cancelled TV show it could be hard to generate new content to post to really help it take off. It would be nice to see people engaging with old posts when they stumble across a community and subscribe to it.
I feel like I haven’t see it a ton yet but I hope it’s a way Lemmy and the Fediverse can be different from sites like Reddit.
There is also the option to sort by “active,” which is not exactly what you are describing but makes it more likely to see older content. Some apps default to this sorting mode