At low n (n < 15-20), electron transfer in collisions between K(np) Rydberg atoms and SF6 can lead to formation of bound K+-SF6- ion pairs that orbit at relatively large separations. A fraction of such ion pairs subsequently dissociate through conversion of internal energy in the SF6- ions to translational energy of the ion pair. The lifetimes of these ion pairs are measured by observing their dissociation. The data show that while the majority of the ion pairs have lifetimes of similar to 1 mu s, some can have lifetimes of 5 mu s or longer, much greater than their anticipated orbital periods, similar to 20-150 ps. (C) 2008 Elsevier B.V. All rights reserved.