Sed festival
The hypothesis of a reign more than three decades long for Nyuserre Ini is supported, albeit indirectly, by reliefs discovered in his solar temple showing him participating in a Sed festival. This festival was meant to rejuvenate the king and was normally (though not always) first celebrated after 30 years of rule. Representations of the festival were part of the typical decorations of temples associated to the king during the Old Kingdom and mere depictions of it do not necessarily imply a long reign. For example, a relief showing Sahure in the tunic of the Sed festival has been found in his mortuary temple, although both historical sources and archeological evidence agree that he ruled Egypt for less than 14 full years.