It is uncertain exactly how long snapping turtles can live, but they can reach 30 years or so in the wild.

In captivity their lifespan seems to lengthen and it is believed they can reach 45 or 50 years.

The record seems to belong to a specimen kept at the Philadelphia ZOO until its death at 38 years, 8 months and 27 days (1979, Pritchard, Encyclopedia of turtles). For certain, regular feedings and good maintenance prolong the lives of any kind of turtles or tortoises.

On the other hand, life of many snapping turtles in the wild is very short. They are very vulnerable as hatchlings, and are preyed upon by all kinds of predators such as birds, ferrets, cats, dogs, other turtles etc.
The main predator of an adult snapper is humans.

Turtle meat, considered a delicacy in many parts of the world, is in great demand. For this reason large snappers are hunted for meat in the wild. Fortunately, there are now a number of farms raising snappers commercially for food and their shells.

Also, because of their appetite and the belief they contribute to the decline of local fish stocks in some areas, a number of snapping turtles are killed every year by anglers who consider them nothing more then pests.

Sometimes, for not a well trained eye and having the same name ( it is in fact difficult to identify a turtle species looking from a distance at an animal in a murky water and covered with, sometimes quite large in wild turtles, amounts of " moss " on their backs ), the alligator snapping turtle is taken as a common snapper, and the other way around.
They both, close relatives, belong to the same family, yet their shells and bodies are quite different. The main difference, not easy to discover it unless the animal opens its jaws, is the presence of a fleshy pink worm - like body at the bottom of the alligator snapping turtles mouth. I have seen quite few pages on the Net mixing up the two species, mostly with the common snapper being given the description of an alligator snapper.( sometimes the text, given information and the turtles picture don't match )
As a result of this, some estimations of a turtles age or size given by people might not be correct at times. Not that the people are doing it out of ignorance, but simply in many areas the terms " snapping turtle " or " snapper " mean and are identified with the alligator snapping turtle only.
What might be true to the alligator snapping turtles is not the truth for the common snappers,
and vice versa.
The alligator snappers grow much much larger than the common snappers and live much longer lives. Considering their slow pace of growing at very large sizes, around 200 lb., their age probably exceedes 100 years.