SSL comes in two strengths, 40-bit and 128-bit, which refer to the length of the "session key" generated by every encrypted transaction. The longer the key, the more difficult it is to break the encryption code. 128-bit encrypted messages are 309,485,009,821,345,068,724,781,056 times harder to break than 40-bit messages. Thus, it would take the same technology used to crack the RSA 40-bit message 1 trillion x 1 trillion years to crack a 128-bit message. That's several trillion times longer than the age of the Earth.
Probably long enough for those credit card numbers to be expired by the time your encryption is broken.