We have many places where users make a decision to use a certain format, property or any other option and expect this to be default for the next time. Storing the last used value until the user changes it again might also make several options obsolete.
Heiko, isn't this the same as Bug 126501 (UserChoice) - [META] Remember last user choice?
Or Bug 109265 (Dialog-Remember-Settings) - [META] Remember dialog's previous settings issues?
*** This bug has been marked as a duplicate of bug 126501 ***