When our forever DM had a kid I ran a side campaign for a while while he figured out how life works with a kid. He played a character a bit like Kenny from South Park so we could just kill him at a moments notice and he could jump over to child care. Then he got the itch and started DMing again.

After his 2nd kid we started switching off. So I run one week and he does it the next. Now we have 2 not-exactly-forever DMs.