Well, here's the short answer that most people don't like: Technically speaking, and by definition, yes.
A paper co-authored by S. Stancliff, J. Dolan with The #RoboticsInstitute, #CarnegieMellonUniversity, and A. Trebi-Ollennu with the #JetPropulsionLaboratory titled "Planning to Fail - #Reliability as a Design Parameter for Planetary Rover Missions" actually makes the argument that the high degree of reliability built into the MERs far exceeded the 90 day requirement and that has come at a high cost. In this case, they have in fact "bought" reliability. See Abstract below.
Abstract—The Mars Exploration Rovers (#MER) have been operating on #Mars for more than three years. The extremely high reliability demonstrated by these rovers is a great success story in #robotic design. This reliability comes at a high cost, however, both in the initial cost of developing the rovers and in the ongoing operational costs for their mission extensions. If it were possible to design rovers with reliability more in line with their mission requirements (in the case of MER, 90 days), considerable cost reductions could be achieved. This will be even more important for future planetary robotic missions due to greatly increased mission durations.