We studied the effect of superdislocation velocities on thermal hardening of alloys with the L12 superlattice. We estimate the activation energy for self-stopping of dislocations due to changes in the elastic field of moving dislocations as compared with immobile dislocations. We calculate the velocity of a dislocation loop element, taking into account interactions with dislocations. We show that, because of deformation stress, superdislocations can move at nearly the speed of sound. This, in turn, can help reduce the activation energy for self-stopping processes of superdislocations by a factor of 1.3 to 5.