I have built an enormous number of packages for this project over the past few weeks (just over 60) and wondered if a conditional split case without a destination was efficient.  I have been using the Conditional Split component with one case going nowhere as a way to 'throw' out records I don't want.  I guess it isn't until you see something over and over and over again that things come to mind.  Its much like looking at a word you hear all the time and wondering 'is that how you really spell it?'.  I did a little test using the performance monitor counters that come with SSIS.  I looked at the buffers (memory,in use, spooled) as well as flat and private buffers (in use, memory).  To my surprise, a destination for a given case within a Conditional Split is not necessary for efficient memory use.  I am guessing that when you build your SSIS package, the build process sees there is no follow on flow for a given case and tosses the buffers out instead of keeping them in memory.  I'm glad to see I don't have to go back to old packages and add a Trash Destination to all of those Conditional Split components :)