In blues class on Wednesday we practiced string together riffs in the same key bit in different positions. for example, when doing 12 bar blues in the key of A, the first 2 measures of A can be a riff using an A-minor-pentatonic scale in one position, then the 2nd 2 measures of A can be out of an A-minor-scale in a different position, either higher or lower on the fretboard. This adds variety to your riffs. You can do the same with the 4 (D) and the 5 (E) of the 12-bar blues.