Those plucky Mars rovers are still going. Their planned roving time was three months but now more than four years in, NASA is sending Opportunity off on a two-year trek to visit a large crater.
The mission team estimates Opportunity may be able to travel about 100m per day. But even at that pace, the journey could take two years. The rover will stop to study rocks on the way, and in winter months it cannot move because there is not enough sunlight to provide sufficient power for driving.