It's rather implausible unless you remember a good deal of the password already, or you are certain that it followed a particular pattern. Even on a good processor you might only be able to try 10 variations a second, which is uselessly slow for anything in the password cracking world.

It needs to be strong, the encryption is designed keep your coins safe.

How much is at stake? Recovering them might not even be worth the time expenditure.

Using brute force you won't be able to recover your passphrase within your lifetime, but you can use vanitygen to recover it (well it won't be you who recover it, it will be your grand grand grand .... sons who will finally recover it)