Renewable resources

Renewable Resources is a term for any resource that can be resupplied without the use of hacks, cheats, or exploits.

Age of Empires
In the original Age of Empires, it is not entirely possible to have renewable resources, however in theory, Food would be infinite (in the long run) but is barred by the Finite amount of wood generated or placed by the scenario creator. Gold through trading is also in theory, infinite (in the long run) but is barred by the lack of other resources.

Age of Empires II
In Age of Empires II (or the Age of Kings) the Exchange Feature was added, this allows the player if they ran out of resources, to be able to exchange gold (from trading, if there IS an ally) into wood, for gold, because of this the player can get an infinite amount of gold through trading, which in turn can be exchanged for wood, which can be used for Fish Traps and Farms which can then be exchange for Gold, Stone and Wood.

The Portugese Feitoria can also be used to slowly generate all resources.

Age of Mythology
Age of Mythology still uses the exchange feature from Age of Empires II, which allows you to exchange food for gold and wood and vice versa. Along with the continuation of Land-based Trade (which can now trade between your Market and Town Center rather than just an Ally's)

Favor a new system introduced allows the player to infinetly gather favor:
 * Greeks pray at their Temples
 * Egyptians can build Monument, which slowly generate favor.
 * Norse can train Hesirs that slowly regenerate favor, along with the ability to gain favor as a Bounty from killing enemies (as long as there is an infinite amount of enemies)
 * The Atlanteans can generate favor by building Town Centers, which slowly generate favor.
 * (the following is unreleased, and maybe subject to change) The Chinese can build Gardens which function like the Rice Paddies from Age of Empires III, but can also generate favor slowly.

Age of Empires III
Like Age of Empires II and Age of Mythology the exchange feature returns, along with the ability to farm food from Mills. A new building called the Plantation, allows your villagers to gather gold from them (like the mill) Whales also provide an infinite amount of gold (although it only allows 4 fishing ships to gather from it at a time)

Building Trade Posts and researching "Stagecoach" allows you to switch between resources. The new Experience system allows people to infintely gain experience by training units, building, and killing enemies.