Soda cans can stay fresh for up to 9 months at room temp. If kept in cooler conditions (e.g. refrigerator), this can be as long as 12 months That freshness is in large part driven by the carbonation and flavor compounds, both of which are sealed safely away together inside a convenient aluminum container. As carbon dioxide permeates the seal on a can, its level of carbonation goes down over time.
Research by the Can Manufacturers Institute shows a loss of 10% over six months in soda cans. This number falls to about 70% at the nine-month stage - all pointing toward how much life and vibrancy has decreased. In fact, industry giants like CocaCola and PepsiCo tell us this is the best period over which to enjoy their products.
Storage is another consideration as chemicals in cleaning agents can spoil more quickly if they're heated or exposed to light. For example, soda cans that are stored in a hot garage during the summer may go flat more quickly than those stored inside of a cool, dark pantry.
The aluminum used for the production of soda cans, plus many aspects canceling in particular, which significantly affects keeping quality. Aluminum is the material of choice because it is lightweight, non-corrosive and an excellent oxygen- and light-barrier. The interior lining, typically a polymer resin used to guard the liquid from copper contact that can cause leaching of off flavors and lead contamination.
According to industry standards, users should look at the expiry date printed on the bottom of soda cans for best freshness. Drinking soda after its expiration date is unlikely to make you sick, but it will be flat and unpalatable.
As for the question being asked about whether can soda last indefinitely, it is important to realize that although the cans themselves may be able to remain rust and corrosion free still through many years of storage if kept in a good condition like not pressurized or over-pressurize with CO2 gas while under compression from freezing, but there will some degradation loss occurring gradually on their internal liquids too.
So in summary, the durability of soda cans is determined by factors such as storage conditions, can seal quality and time since packaging. For optimal taste and carbonation, soda should be consumed within the recommended 9 to 12 months from date of production.