🚀 go-pugleaf

Try the following solutions:

-Rebuild the desktop by holding down the Command and Option keys
 together as you restart your Macintosh. This creates a fresh 
 desktop file that may be more efficient than the one that 
 currently exists on your computer.

-Use a de-fragmentation program, such as Disk Express from AlSoft,
 to optimize the file organization on your hard disk. As you add and
 delete files from your disk, the amount of continuous open space
 on the disk becomes smaller, and files have to be broken up and 
 spread across several segments of disk space to fit on the disk.

The desktop file is an invisible file which maps out the hard disk, 
and the fact that it takes so long for your mac to update the disk
indicates the Desktop directory is either very large, very complex, 
or damaged. It's unlikely this is a hardware problem. You might also
run Apple's Disk First Aid before running the above programs.