The thing is, you don't actually care that much about your "gold stockpile", mostly you ensure that there is not a net loss.
In the Total Annihilation/Supreme Commander games, it's more like a regular RTS resource: you use it up, until you have none left, then wait for it to trickle/fill up depending on how many extractors you have. Since you're not always building, your stores just fill to capacity,
If your ever finding you were filling to capacity then you weren't building enough. Generally in multiplayer games it acted more like flow resources in that you'd try and keep something close to net +ve but sometimes dip under and just endlessly build.
It differs in that this was for building and not an ongoing cost.
Civ 5 also uses flow resources for it's stragegic resource model, this time terrain based rather than building.
The Anno series also uses flow resource, I think since the first one back in 98, and is much closer to what you describe although in this case it's some buildings that require the resource and others that generate (and some convert).
Arguably the industry giant games also used this concept although they were more unit resources being moved around than resource totals, like wise the simcity series treated power and later water this way.
Sticking to RTS games there are fewer examples though, even if most have some form of food / popcap which is a flow resource.
The addition of the gold buffer is a nice touch though, may have to get it and see how well that works.
