This is 'straight up math', however - you can expect losses in RL radars. Hpasp's calculation is probably most accurate since it automatically accounts for the losses of one radar at least.
Also, once jammers enter into play (And they will, since each F-22/F-35 is practically its own stand-off jammer) you can see that range shrink into uselessness. It's important to keep in mind that as neat as things look on paper, in reality warfare uses a lot of assets that will not be friendly to your operations.
In addition, the required sensitivity is so great that it will be relatively easy to make a stealth aircraft 'dissapear' again. That's the real strength of a stealth aircraft.
