One of the things you do in a tribunal hearing is read how you’re coming over to the panel. Then you can adjust your approach accordingly. If they are with you on an issue, you may want to quit while you’re ahead. If they’re not you may want to redouble your efforts (or move onto a new point). The ideal is to spend the minimum time on matters where the tribunal is already convinced (or cannot be convinced) to focus on the areas where you may change their minds.
The problem with this is that it is easy to misread the tribunal.
The most damaging result of this is that you move briskly over an area – thinking that the tribunal agrees with you – when you should be dealing with it in detail. This leads to the horrible sinking feeling when you later realise that the tribunal was not convinced at all.
Of course, it is equally possible to speak on length on something that the tribunal is already convinced of. But this tends to be less damaging. This is partly because over-convincing someone of something is normally better than failing to to convince them at all. It is also because the tribunal is more likely to step in to move you on from a point they agree with than to ask you to go back to a point that they disagree with.
There is no absolute solution to this problem. You could simply deal with every point in exhaustive detail, regardless of your reading of the tribunal. But this is likely to do do more harm than good. A concise, punchy submission focused on the areas that the tribunal is in doubt, will be more convincing than anything approaching exhaustiveness.
Like many areas of advocacy, the only thing to do is to be aware of the potential problem and aim at a happy medium. Remember that, in the absence of a clear steer, it is hard to be certain what the tribunal is thinking. Be prepared to err on the side of caution, particularly on an important point. But try not to over-correct and risk boring the tribunal, losing momentum and obscuring your best points.