Updating key expiration in GPG for stripped keys

1. mount airgapped device
2. killall gpg-agent
3. export GNUPGHOME=/path/to/master/gnupg
4. gpg --edit-key key-id
5. expire, set to 6m
6. select subkeys, expire to 6m
7. save
8. test with gpg -ea > secret.out; gpg -d secret.out
9. export gpg -a –export KEYID > gpg.public
10. killall gpg-agent
11. import to stripped keys, private keys never expire
12. publish gpg --keyserver keyserver.ubuntu.com --send-keys KEYID (also to keys.openpgp.org, pgp.mit.edu)