Sometimes a factory built wheel is just garbage. Sometimes not. A good, hand built wheel should last for many years of normal use without ever seeing a spoke wrench. I bought a set of wheels a few years back and had all kinds of problems with the spoke tension. I ended up taking all the spokes out, buying a new set and then building it up by hand myself. That wheel lasted me several years of hard mountain biking and never needed to be trued after the initial build. If there hasn't been any real trauma to the wheel then just have the spokes relaced by hand and all should be fine.