Remember that you can create the corridor text in one of two ways: by putting text into the corridor's text box, or by interrogating the PSX weather model.
When you manually cut-&-paste winds from your flight planning document into the corridor's text box (or when you otherwise write, edit, or submit text to that box), you are telling PSX what you want the winds to be at those points. That data will only be updated when you update them. In the case of realistic, real-world long-haul flight plans, those winds from the flight planning documents are forecast winds. There is no guarantee that the forecast winds will mimic the actual winds, but since these wind forecasts are only updated every 6 hours in the real world, it's usually not practical to ask the flight ops office for a new winds aloft forecast while enroute. By the time the new forecast would reach your aircraft, you're there, and you know what the winds are. :-) Plus, they're forecast anyway, so the accuracy isn't expected to be 100%. So in the real world, you would get one set of forecast winds during the flight planning phase, and in PSX you'd cut-&-paste that wind forecast once into the corridor text box. Of course, if you get an updates forecast from your dispatch office, you could repeat the cut-&-paste into PSX. But PSX won't update the corridor automatically - you would have to do it.
Similarly, when you create the text corridor by interrogating the PSX weather model, that text will only be generated (and the corridor defined) when you ask PSX to create the corridor's text. In other words, the corridor is only created or updated when you ask it to be created or updated. However, in the second case, the corridor comes from the PSX world, and that weather within the corridor may change. The upper wind model is dynamic, in that the winds aloft are created from an interpolation between the METARs at the surface and the PSX jet stream model at the tropopause. In this case, as the METAR's change over time (and/or if you change the jet stream by dragging its indicator line), the winds aloft within PSX would change. So the winds over Dar es Salaam might be different at midnight than they were at noon. But the actual text corridor won't change until you interrogate the PSX world again, and ask for a new corridor text to be generated.
(Hardy will correct me if I'm wrong.)
