The fact that the state of the art has been inactive over a long period prior to the invention may be an indication that an inventive step is involved if during that time an urgent need for improvement has demonstrably existed (see T 109/82, OJ 1984, 473; T 555/91, T 699/91). This indication is closely linked to the positive indications of the time factor and age of the cited document.
In T 605/91 the board stated that it was not sufficient if only one individual skilled person discovered a "long-felt need". Only if various and repeated attempts to deal with the relevant disadvantages could be identified would such a long-felt need appear to have persisted.
In T 1014/92 the board did not accept the appellant's further argument that the long period of time (about 35 years) during which documents (1) and (2) had been available to the public without having been combined, was in itself cogent evidence that there was no obvious connection between them. The board held that this conclusion might only be drawn if evidence relating to time were corroborated by other evidence, such as long-felt want (see also T 1183/06).
Where a process had been performed successfully on a commercial scale for more than 20 years in spite of economic disadvantages associated with it, and the claimed invention provided a solution to the technical problem of avoiding such economic disadvantages, this supported a finding of inventive step (T 271/84, OJ 1987, 405).