Honestly, I never bother. If something takes 4 milliseconds to load or 8, I have the 4 milliseconds to spare.... remember the programs RUN in the RAM. Defrag doesn't make your programs RUN any better, just load a bit faster. That rare occasion that something gets crosslinked doesn't worry me. I trust my FAT to do it's job.

But that's me and my opinion. Defrag your little heart out if you like.