Interspersed fatigue (pulsating flexing) and creep (dwell time) cycles were applied to samples of natural and butyl rubber at room temperature, lab-air conditions. In this experimental program the natural rubber was found to be sensitive to the application of dwell times under peak load conditions. Cavities and cracking were observed as a result of dwell time lowering its resistance to interspersed fatigue and creep cycles. On the other hand, flexing resistance of butyl rubber was found to be inferior to natural rubber. These results are presented in this technical note.