Thank you for your post.
Even though the customer may be doing simple logging, behind the scenes, even if the customer isn't using those fields, the lookups and relationships are still active.
One option is to create a script that opens all database files and hides them. Then, you can execute the script when the file is open. Once open, the user doesn't have to worry about waiting for the other files to open. Likewise, when you close the file, you can execute a script that closes all files. To set these scripts, pull down the File menu and select "File Options..."