Repeating for an Indeterminate Length

I notate a lot of "groove" based percussion music, specifically Brazilian rhythms. The rhythms are often two bars long and just repeat themselves ad nauseum, for an indeterminate length. Any suggestions on the best way to notate this? I've tried putting the whole phrase between the "Start Repeat" and "End Repeat" barlines and creating a text box that says "x?" I've attached and example of this. Any other ideas?