time delay unlock private key.

[Robert J. Hansen]

> My private pgp and smime keys are secured by a password, but there is no
> time delay, which makes a brute force attack possible.

GnuPG doesn't make a brute force attack possible.

You make a brute-force attack possible by choosing a weak passphrase.   
Choose a strong one.  It's really that simple.

> Could a time delay be implemented similar to the one I just mentioned?

Not really, although DKG gave you a good heads-up about the number of  
iterations in s2k.