XPS 8930, hybrid SSD/HDD defrag?

So C drive with SSD is shown to have system OS and applications and the D drive with the HDD has the data files.  I'm surprised that the 1tb HDD only has 5.3 gb used.  The 256gb SSD has 101gb used.  So I've seen many sites recommending that a SSD never be defragmented as it reduces the lifespan.  Thoughts?