There will likely be a great many genetic contributions to human longevity, as this open access paper suggests, which in turn means that the genetics of longevity will be a very complex morass of a field: "The results of genome-wide association studies of complex traits, such as life span or age at onset of chronic disease, suggest that such traits are typically affected by a large number of small-effect alleles. Individually such alleles have little predictive values, therefore they were usually excluded from further analyses. The results of our study strongly suggest that the alleles with small individual effects on longevity may jointly influence life span so that the resulting influence can be both substantial and significant." Bear in mind that this may mean thousands or tens of thousands of potentially important interactions, which may differ significantly by population or individual. This is one of the many reasons that slowing down aging will likely be harder to accomplish than repairing the effects of aging: a repair strategy such as SENS doesn't depend on understanding genetic contributions to longevity. Researchers already know enough about the varied forms of biochemical damage that cause aging to make a start on repair technologies, were they so minded.