It took the Curiosity rover just over eight months between launch/landing on Mars, arriving there on August 6, 2012.
Even with the phenomenal success and longevity of Opportunity at that time, Curiosity's mission was only slated for two years.
Keeping in mind, however, Curiosity's development began in 2004, the start of Opportunity's mission. As such, that was the starting point for the technology going into Curiosity.
In 2004, all hardware features and instrumentation had been chosen and testing and integration of the individual components began. While the freeze on hardware features meant that no new or additional significant hardware components were going to be added to the rover, it did not mean that newer technologies could not be implemented as part of the existing features.
It is a fairly simple process in the lab to upgrade/alter an existing piece of hardware or software and often is a requirement during the integration and testing phase of the various components. As far as the computer itself is concerned, ir stays pretty much the same throughout the development cycle as the programming has been written specifically for that computer with all of the limitations of that computer taken into account. Individual chips within the computer, however, may be replaced/upgraded to correct issues which are found during testing as long as the new component is functionally identical to the part being replaced.
That being said, while it is accurate to state that the rover is 'based upon' 10 year old technology, many of the components themselves in the computer are actually much newer than that.