The book Roughneck Nine One provides an excellent description of the Javelin being used under combat conditions for which it was intended (ie anti-tank rather than busting houses). The account describes Javelin's advantage which, as it turns out, can be a liability. Its ability to kill AFVs actually exceeds paper specs with respect to range according to the book (from a security perspective I was surprised to read this in a mass market book). As for flight time the crew first thought there had been a mis-fire since, from their perspective, the missile simply vanished into a low cieling for a very long period only to come down right atop the target. But the operators also had some difficulty achieving lock when an insufficient amount of the target's hull was visible.

So Javelin's long flight time is not as important to the crew since they were able to exploit the missiles homing ability and shoot-n-scoot if desired (they stood, fought, and won in the actual event). But that same human-independent homing ability was clearly less capable than the human eye and judgement.