They can go a damn site longer than that, I travel for work a few weeks at a time and im lucky if my wife remembers to feed my fish twice during that time.
Most fish are good for two weeks just picking off the pods and whatnot, not that I encourage that, but they are a lot tougher than you think. If you loose a new fish due to starvation, odds are it hasnt eaten for a month or so.
Exporters stop feeding a week before they ship to they dont pollute the water, the collects dont feed them because it costs and they don't keep them long enough to worry about it. By the time they get to QT they are stressed and havnt eaten for several weeks so can continue that habit quiet easily, they are also at their most vulnerable to any parasites and whatnot.