I don't really agree Question RSS feed, or any feed for that matter, should worry about showing recent items. It should always show every item and leave the rest to the aggregator. But maybe it could give an option, such as http://meta.stackoverflow.com/feeds/question/22374?startdate=yyyy-mm-dd to filter out everything before that date.
I hope I'm not going too off-topic on the lines below.
As a side note, I just went to a old question that got several updates and even by ordering it by Newest or Oldest it's got hard to keep track among answers and comments.
While RSS doesn't solve this issue, I think it could if it added comments on it (currently the feed doesn't show the comments). So we could see answers and comments mixed in the order they were posted.
So the Question RSS should look a lot like the question expanded timeline. It's a hidden feature I just found out about, even if it's been around for a little while.
The timeline is also a perfect example of another basic feature that's available in places SO is using as reference such as Digg, Wikipedia, but the developers don't see any reason to implement it at first.