You're looking at lifespan between two and eight years. Gerbil longevity depends on which species you own, how well it has been looked after, and what diseases it contracts during its life.
With a suitable, quiet, clean place to live, in which the animals can exhibit their normal wild behaviors, with all the water and healthy food they need, a gerbil will live a long life, in pet rodent terms. Mongolian gerbils usually live between two and five years, whereas Fat-tailed gerbils tend to live for slightly longer, generally somewhere between five and eight years.
Keeping a gerbil happy and healthy is the key to longevity
Gerbils kept in poor conditions will usually fall ill - but even the healthiest pet can sometimes be unwell, too. There may be some treatments a vet can offer, but sadly in some circumstances there isn't anything that can be done. The best thing to do is to look after your little friends and give them the best life possible for the time you have together.