I'm tempted to suggest binning by arbitrary date time intervals rather than evenly distributing the points and building up intervals.  I haven't followed if we have an IndexedSeq (i.e., backed by an array) or if we're likely to have a LinkedList.  In the later case, size/length is 'expensive'.  

(Sorry, just having an allergic reaction to size.)

Also, in general, I can imagine that tube select inputs might be somewhat regular...