The low-temperature plasma recombination of H3+ and D3+ ions with electrons partially occurs by three-body assisted (ternary) mechanisms that need to be better understood. Intermediate high Rydberg states are expected to play an important role, but it remains unclear which of their interactions with ambient neutrals and electrons enhance their decay into neutral products. This contribution discusses several proposed models, collisional radiative, collisional dissociative recombination, resonant electron capture, and angular momentum l-mixing. It appears that none of them provides a satisfactory explanation. There is one observation that points to a possibly efficient route to long-lived collision complexes that may play a role: Several of the so far unassigned peaks in storage ring data occur at energies where rotational resonances have long lifetimes. A tentative model, based on complex formation and collisional stabilization, leads to qualitative agreement with experiments.