I'm quite prolific when using Agents, and that's probably exactly what you want :). After just a few weeks of enabling agents in one of my projects, opening my .specstory/history leads to something like this: (long image posted with intent, feel it :) )

Ideally, I'd like anything older than 3 weeks to be moved in a monthly directory.

And of course I'd ask an agent to make a "summary.md" file which combines what's been going on during that month in my project. This would help future agents to faster and more efficiently narrow in when changes occurred.

And a tiny voice is telling me that another dimension of this history feature is going to involve classes / directories in the project, but that's for the future. But as we all know, the future is around the corner ;)