I made the calculation of "forever" via internet-time-units. It was longer than a year. According to Wikipedia, it was... 2004.

But seriously, you're right that the challenge is in actually designing a good UX for yourself. You've got four months to mimic Reader if that's what you want to do. I'd suggest XSLT, since RSS actually predates JSON, it's so old. That doesn't allow for any potential mistakes by RSS creators, though, which might be hairy. /shrug