How to change Auto Expire?

[petzi53]

The FAQs states: "To control the age of articles to auto-expire, change the “Expire articles older than” option in Preferences." But I cannot find this option in my installation. I am using Version 3.4.2 :7bc20f57: (6905) with a German MacOS HighSierra version 10.13.6 (17G65).