The search for new elements is part of the broader field of investigations of nuclei at the limits of stability. In two series of experiments at SHIP, six new elements were synthesized via fusion reactions using 1n-deexcitation channels and lead or bismuth targets. The isotopes were unambiguously identified by means of correlations. Alpha decay, not fission, is the dominant decay mode. The collected decay data establish a means of comparison with theoretical data. This aids in the selection of appropriate models that describe the properties of known nuclei. Predictions based on these models are useful in the preparation of the next generation of experiments. Cross sections decrease by two orders of magnitude from bohrium (Z = 107) to element 112, for which a cross section of 1 pb was measured. The development of intense beam currents and sensitive detection methods is essential for the production and identification of still heavier elements and new isotopes of already known elements, as well as the measurement of small -, - and fission-branching ratios. An equally sensitive set-up is needed for the measurement of excitation functions at low cross sections. Based on our results, it is likely that the production of isotopes of element 114 close to the island of spherical superheavy elements (SHEs) could be achieved by fusion reactions using targets. Systematic studies of the reaction cross sections indicate that the transfer of nucleons is an important process for the initiation of fusion. The data allow for the fixing of a narrow energy window for the production of SHEs using 1n-emission channels. The likelihood of broadening the energy window by investigation of radiative capture reactions, use of neutron deficient projectile isotopes and use of actinide targets is discussed.