ihmatthews comment
"No, I don't link the media files (aka images) to FTM. I download them, logically name the file and store them in a genealogy folder and subfolder computer filing structure I created in Windows. Any pertinent facts are posted and sourced in FTM without a link. I had thousands of files in my genealogy computer filing system before I had the FTM media feature available. I considered it and dismissed the idea of trying to link all the files already downloaded or scanned(over 20,000)."
My process and methodology is very similar to yours and for essentially the same reasons.
I do do a couple of things that I think help me
1-I use the same EXACT title for my Image Title as I use for my FTM Source Title [I have devised the titles of my sources so that they fall into "natural" categories. I have requested an enhancement several times,to no avail, to have FTM have the capability to categorise sources just as they have done for images]
2-I categorize/sort/store my images in Windows folders/subfolders using a similar concept as the FTM 2012 Image file category concept [I have done this because it seems to work quite well and maybe someday FTM will be improved enough to link my images to it]
1 and 2 help me considerably when for example I have a source documented with facts and I want to look at the Image to see if I missed something, etc. I have three screens [2 25's and 1 30 inch] so I can look at the Image on one screen and simultaneously look at the FTM source/fact/attribute [person window] info on the other screen
Basically I don't link the image to the source computerwise because it will slow down the program and links are very easily broken. For example, suppose you had linked your thousands of images to FTM and then you moved/changed you image file ----all your links would be broken