Have a setting in the feed builder to only show pages updated since last check

Currently Confluence renders the last n pages that match a user's feed. This can cause problems when users have feeds that show the last 100 updated pages and request that every 15 minutes. This is resource intensive even if they are simple pages.

As the amount of content increases in a confluence instance, users who want to keep up with many spaces tend to increase the item limit and shorten the duration between updates so they don't miss out on new pages/blog posts/comments. This is not scaling very well for us.

It would be nice if there is an option in the feed builder to see "only give me pages that have changed since I last checked the RSS feed". That way, even if users check their feeds every 5 miutes, confluence only has to do a (relatively easy) "last modified since" check rather than render the last 100 posts.