It should not take that long. As to why - without more information it's pure guesswork.
I suggest you put all the system information in your signature (see mine below.) Then it's always available when you ask a question.
Dell Precision T7600 (x2)
Win 7 64-bit
Adobe CC 2017.1 (as of 8/2017)
256GB SSD system drive
4 internal media drives RAID 5
Typically cutting short form from UHD MP4, HD MP4, and HD P2 MXF.