>JPEGs are compressed files that uncompress when you view them and >them recompress when they are closed. Like a spring, they >eventually deteriorate over time.
This is incorrect. Opening and closing the JPG files is not a problem. You are just reading and uncompressing the same data over and over with no changes to that data.
The "damage" happens when you change the data and save the data back to disk as a JPG. It is the saving that does another round of destructive compression. It is the repeated cycle of open-edit-save-close that is bad for jpg files. You can do open-close forever with no loss of data.
The advantage of TIF and other losslessly compressed files is that the edit-save loop can be repeated with no data loss.
---------+---------+---------+ Joseph K Seattle, WA, USA