Most Giant African Land Snails, given a healthy lifestyle and good care (and not too much beer!) tend to live about six years, although they can live up to ten.
Size
Size varies with each species. Achatina fulica grow to an average of 10cm; Archachatina marginata grow up to 15cm, and Achatina achatina can reach an astounding 20-25 cm. These measurements are of the shell, not including the body! The rate of growth can depend on temperature and activity, but the snail will do most of its growing in its first year of life.
You will be able to tell when your snail has reached its full adult size when the area at the bottom of the shell develops a pronounced curved lip.
Breeding
Snails are hermaphrodites, which means that they contain both male and female reproductive organs. However they cannot impregnate themselves, and you will need to have two snails of breeding age in order to get them to reproduce.
After shooting each other with a spermatophore (love dart), the snails will lay a clutch of eggs in the soil. Achatina fulica and Achatina achatina can lay a few hundred eggs at one time, although other species lay far fewer. The best thing to do with the eggs if you want a successful brood, is to remove them to another container, to prevent the adult snail from disturbing them. Keep them nice and warm (24 - 26 degrees c) and the eggs should hatch after about15 days, and should be kept in their own tank until they are a little more robust. Remember to keep checking for eggs or you'll be over-run!
Archachatina marginata only lay a few eggs, but they are much larger in size. It is inadvisable to move these eggs. Simply place an upturned glass over them to keep them free of disturbance.
Illness