It doesn't really matter with PGP, that is what I was trying to say. It is a technicality. Technically, message length correlates with the time it takes to decrypt a message, I believe in every possible case but don't quote me on that. When a message is encrypted with PGP, what really happens is that first a random session key is generated. The plaintext message is then encrypted symmetrically with the session key. Then the random session key is what is encrypted with RSA, the session key will be either 128 bits or 256 bits depending on the symmetric algorithm used. The final ciphertext block contains the asymmetrically encrypted session key as well as the symmetrically encrypted message. After the session key is discovered, it is fed into a symmetric algorithm. The best example I can think of is counter mode AES which is a stream cipher, block ciphers work differently but I think the same thing will apply. With AES in counter mode, you feed the algorithm the session key and then it outputs a key stream. You obtain the plaintext message by XORing each byte of the ciphertext with the matching byte outputted from the AES algorithm that you fed the session key to. So a bigger message means that the AES function needs to generate more bytes, and more XOR operations need to take place, so technically it will take longer to decrypt a longer message, but it isn't significant.