Modern AA missiles are not RPG's. They are very, very expensive. Even a simple AIM-9 is the equivalent of launching an extremely fine sports car off your rail in terms of cost. I cannot imagine launching salvos of even more expensive long-ranged radar missiles in some "fire for effect" method. It is unlikely they will even be detected or seen at such extreme ranges.
Besides, if this technique is used, a simple counter (which has in fact been used for decades) is to run decoys in first who will drag out, escape, at the edge of the missile envelope. Fired missiles are defeated kinematically, while those bringing up the rear behind the decoys can then engage.
Missiles lose energy very quickly upon motor burn-out, which is why extremely long-ranged missiles are lofted high into the atmosphere, where there is less drag, and they can come down on a target. Still, as range increases, the likelihood of a successful intercept drops.
Secondly it is often said that one who makes enemy fight on his terms has high probabilty to end up winner. Don't you think with detecting the enemy first even though missiles cannot be launched is going to increase the odds???
Unless you are executing a sweep, you will almost always have a threat axis, a known area where the targets will either come from, or are defending. Airspace in an air battle is usually cut up into slices, with areas of responsibility.
Let's say there are strikers inbound. Your super-radar sees them at 300 km and the aspect is 10L, flying nearly perpendicular to your axis. At 300km, you will not have any hope of intercepting them unless they turn into you. Others defending the airspace along their axis will have to make the intercept.
I'll try to summarize: At the range where there is a decent chance of a successful launch and missile hit, the likelihood that both sides will know the other is there is very high; further, extreme detection ranges rarely allow one to alter how the encounter will happen. You'll get faint and irregular hits at first, then someone in the flight will take a sample lock, enough energy to tickle the target's RWR. His RWR will display a threat at, say, 10:00, and he has the choice to disengage (turn 120 degrees right and drag out) or engage (turn 45 left to put the RWR hit at 12:00. His radar will reach out and find you.
Even if his radar lacks the range, he can take the RWR hits and keep them at 12:00. From your perspective, he is keeping nose-on to you. Eventually, he will see you, still outside effective missile range.
When executing a sweep, a flight of four relies much on RWR. If it displays a threat at 3:00 or 9:00, the entire flight will "snap" (turn hard) into the threat, and find the inbound bogies using disciplined radar search.
@Anathema: That is a whole different game. A very complex procedure and I can see much that would go wrong in real life. The missile energy is poor at the end-game; a heavily-jammed environment can create issues.
Here is something to consider for the long-ranged missile shot fans. You've got a target aspect of 14R (40 degrees off axis). You shoot. The missile doesn't fly at the target, it flies to a predicted intercept point which might be 50 km or more well to the side. the missile flies, is 1/3 of the way there. The target then turns hard to 14L. The point of intercept has now physically moved 100+ kilometers, to the other side of the axis. The energy of the missile is gone as it tries to solve this new problem, and falls out of the sky. A simple 60 degree turn by the target has defeated the long-ranged shot.
At closer ranges, that same turn moves the intercept point only 5 to 10km rather than 100+. This, the missile can handle.
I hope all this makes sense. Sorry for the long post.