When I want to contribute to an open source project, I throw together some trivial but useful patches and see how the project responds.

Many projects behave this way, particularly those with corporate overlords. At best, it will take weeks to get a simple patch reviewed. By then, I have moved on, at least with my intention to send anything upstream. I commend the author for giving them a whole year, but I have found that is best a recipe for disappointment.

Maintainers: how you react to patches and PRs significantly influence whether or not you get skilled contributors. When I was maintaining such projects, I always tried to reply within 24 hours to new contributors.

It would be interesting to see how quickly the retention rate drops off as the time to review/accept patches goes up. I imagine it looks like an exponential drop off.

Absolutely. I look at the commit and PR history. Are the maintainers responsive and welcoming?