For some reason, certain apps such as IE11, Firefox, etc., have an annoying tendency to constantly update XXXXX.customDestinations-ms files located on your system drive. Needless to say, this causes un-necessary writes to your precious SSD every few minutes.
The solution:
These files are located at:
C:\Users\%USERNAME%\AppData\Roaming\Microsoft\Windows\Recent\CustomDestinations\
or more simply: %AppData%\Microsoft\Windows\Recent\CustomDestinations\
First sort the files by "Date Modified".
It is perfectly safe to delete old entries.
For recent entries that keep getting created/modified, you can simply set these files as READ ONLY. This will prevent further writes to these files, and help keep your SSD in top shape.
By the way, to check which .customDestinations-ms file corresponds to which app, you can open it in Notepad++, press CTRL+H to perform a Replace. Down in Search Mode, select "Regular Expression", and in the "Find What" field, type: \x00
This will get rid of all the NUL characters, so now you'll be able to more clearly see which app each .customDestinations-ms file is related to. No need to save changes when you close this file.
*NOTE 1: This might work on more recent versions of Windows, but I haven't tested. You're welcome to comment about your findings if you're running Windows 8.1 or Windows 10.
*NOTE 2: I searched for a more elegant solution, such as modifying a registry setting or via GPedit setting, but to no avail. There is nothing that can stop the creation of these files. The above solution is the best for now.