In their earliest history, Kree had a lifespan of roughly 85-120 years. Today the average Kree could potentially live about 250-700 years, though most soldiers are either killed in combat or other dangerous situations. Longer lifespans, up to and including functional immortality, are possible with rare Kree medical science, though notably not the Black End (cancer).
Kree have a unique aging process where they remain in their physical prime for an extended period, allowing them to fight effectively for longer. While their lifespan is comparable to advanced races in the galaxy, they don't experience the same gradual aging process. Instead, they maintain their youthful appearance and strength until a certain age, after which they gradually deteriorate into old age
Upon death, most Kree are cremated (a few still opt for burial); the greatest and wisest of the species (a very small number, these days...) become part of the Kree Supreme Intelligence (see below).