Yet one more reason Simba should've had Zazu watching Kiara instead of Timon & Pumbaa

I think another thing to have in mind, too, when trying to make sense of & considering the hows and whys of aging in the Lion King films, is that there's a difference between average ages in the wild and total possible lifespan in captivity. For example, one hyena in the wild noted for longevity in the field data of Michigan State University researchers, who have been continuously studying clans in the Masai Mara for going on 3 decades, lived to about 18.5 years (18 and some months over half, and her daughter nearly matched her, some hardy genes there!) with 15-16 or so the more common old age death. Meanwhile, just last year, Brownie, the last remaining hyena used as a reference by Disney animators FOR drawing The Lion King, died peacefully in her sleep at the Sacremento Zoo at an absolutely remarkable twenty-eight years old, an all-around amazing run

Yes, the events of TLK take place in a world vacant of humans, but it's also an idealized/utopian wilderness sans parasites where termites are the biggest pests an animal is inconvienced by, and when you take average lifespans in captivity into consideration, the playing field smooths itself out quite a bit. A minty-fresh young adult Timon at one year old could then be looking forward to a solid 11-12 or so more years ahead of him, plenty of time to watch Kovu & Kiara get hitched, especially considering I doubt Kiara's ever much more than a teenager in SP.