Hello. I have the late 2013 baseline MacBook Pro Retina Display with 8 GB of Ram. So, as today the new rMBP with 16 GB of Ram were announced, I feel a little bummed since I paid the same price for only half of the Ram. So my question is how much of a difference is between 8 and 16 GB ? I guess I won't upgrade to the new model but how long will 8 GB last ? I want to keep it for at least 4 years.