I'll bet a thousand dollars Curiosity will last 15 years. NASA seems to have a good track record when it comes to Mars rovers lasting much longer than their intended missions.
Of course, it doesn't change the fact that the Soviets made the first successful (secret) Mars landing in 1978. The landing site was at the highest point of Olympus Mons (chosen for a symbolic reason, obviously). Unfortunately, the collapse of the USSR forced the demise of the Soviet Manned Mars Exploration Program (SMMEP). They only landed on Mars 7 times between 1978 and 1989; after the last crew returned home the project was abandoned due to lack of necessary funding. A permanent base was planned- the hope was to colonize the planet before NASA knew what hit them.