After reading¹² about this subject, I believe a reasonable level of security and ease-of-use can be achieved through the following process:
1. Boot a live Linux distribution such as Tails on a computer disconnected from the Internet.
2. Create the OpenPGP master key.
3. Initialize the YubiKey with subkeys.
4. Store the master key offline using paperkey³ and a machine-readable code.
The YubiKey is secure and convenient enough for daily use; the subkeys can be easily revoked and the hardware reinitialized with new keys.
Master key operations such as key signing and changing expiration dates require loading the master key into the offline live operating system. Much more of a hassle but hopefully not as frequent as YubiKey use.
Printing the master key on quality paper ensures³ it will survive for a long time.
¹ http://security.stackexchange.com/a/51776/9252