The script below does two things:
1. Whenever someone saves the config, a copy of the new configuration is saved into the TFTP server;
2. If no one saves the config for <MINUTES>, a copy of the current startup-config is sent to the TFTP server.
Try the following stuff below.
conf t
archive
path tftp://<IP Address>/Subdirectory/$h-
time-period <MINUTES>
write-memory
end