Slow activity stream on Fisheye dashboard

As reported by a user, the activity stream on Fisheye dashboard can sometimes slow down and run in over a minute. Looking into logs there are 3 lucene queries run by CrossRepositorySearcher#findRecentChangeSets and most often the last query is way slower than first two.

Last query is invoked by StarDownStreamActivityItemManager#hasEarlierActivity and is run to check whether there is any earlier activity on the stream to decide whether infinite scroll should attempt to bring more content.