The right to oral proceedings regulated by Art. 116(1) EPC forms a substantial part of the right to be heard granted by Art. 113(1) EPC (T 209/88, T 862/98, T 1050/09). The right to be heard in oral proceedings subsists so long as proceedings are pending before the EPO (T 598/88, T 556/95, T 114/09).
The right to present comments enshrined in Art. 113(1) EPC does not need to be exercised in writing but may be satisfied by way of oral proceedings (T 1237/07). This does not mean, however, that it is for the boards to ensure, of their own motion, that all points raised at some point in the proceedings are discussed at the oral proceedings. Rather, it is for the parties to address any point they consider relevant and fear may be overlooked and to insist, if necessary by way of a formal request, that it be discussed. If a board then denies the party an opportunity to put forward its arguments, this may constitute a ground for asserting a breach of the right to be heard under Art. 113(1) EPC (R 17/11). This also applies in oral proceedings before the opposition division (T 7/12).
Non-compliance with a request for oral proceedings deprives the party of an important opportunity for presenting his case in the manner he wishes and using the possibilities open to him under the EPC. By virtue of his request for oral proceedings, the party can rely on such proceedings being appointed before the issue of an adverse decision and therefore has no reason to submit further arguments in writing (see T 209/88, T 1050/09; and also Chapter III.C.1, Right to oral proceedings).