Patterns in the buffer usually degrade over time - The TNG Technical Manual says patterns can last about seven minutes before degradation begins. Obviously, Scotty was able to extend this dramatically, though with only a 50% success rate.
They did touch on this in SNW season one, when M’Benga said he had to rematerialize his daughter periodically. However, the timeframe, while not specified, seemed a helluva lot longer than seven minutes.