ErrPs have been used lately in order to improve several existing BCI applications. In our study we investigate the contribution of ErrPs in a SSVEP based BCI. An extensive study is presented in order to discover the limitations of the proposed scheme. Using Common Spatial Patterns and Random Forests we manage to show encouraging results regarding the incorporation of ErrPs in a SSVEP system. Finally, we provide a novel methodology (ICRT) that can measure the gain of a BCI system by incorporating ErrPs in terms of time efficiency.