You mean multiple rounds of password hashing to generate the AES key

http://en.wikipedia.org/wiki/PBKDF2

Repeatedly doing AES does nothing, as AES is designed to be fast and  it is implemented at hardware, like in Intel CPUs

Wallet encryption uses AES-256-CBC to encrypt only the private keys that are held in a wallet. The keys are encrypted with a master key which is entirely random. This master key is then encrypted with AES-256-CBC with a key derived from the passphrase using SHA512 and OpenSSL's EVP_BytesToKey and a dynamic number of rounds determined by the speed of the machine which does the initial encryption (and is updated based on the speed of a computer which does a subsequent passphrase change).