I looked for a similar post to this, but couldn't find any within the last few pages
In Civ3, strategic resources can "wear out" over time, and it appears to be linked to how much time the resource is connected to the Civ, rather than on usage.
An alternate method, which has been used in other games, is to have each resource have a specific starting value, and each time that resource is "used", ala constructing a unit/improvement/wonder, so much of that resource is used. Some resources (like horses) would naturally regrow at a slow rate. You could have city improvements/techs to decrease the depletion rate. Whether the exact resource amount is known to players is questionable.
Another similar idea would be to allow storing the raw materials in the city proper, such that even if you lose the road to that resource, you can live off your stockpile for a bit.
In Civ3, strategic resources can "wear out" over time, and it appears to be linked to how much time the resource is connected to the Civ, rather than on usage.
An alternate method, which has been used in other games, is to have each resource have a specific starting value, and each time that resource is "used", ala constructing a unit/improvement/wonder, so much of that resource is used. Some resources (like horses) would naturally regrow at a slow rate. You could have city improvements/techs to decrease the depletion rate. Whether the exact resource amount is known to players is questionable.
Another similar idea would be to allow storing the raw materials in the city proper, such that even if you lose the road to that resource, you can live off your stockpile for a bit.