Self Service Password Reset Token Validity

Some of our users forget their passwords and then write an email. Instead of sending them a link to /univention/self-service/#passwordreset we tried to initiate the password reset for them. Normally users check their mails too late for the 1h validity of the password reset token. We tried ucr set umc/self-service/passwordreset/token_validity_period=604800, but still get The token you supplied is either expired or invalid when clicking on the link within the same day. Is this UCR variable working at all?