I've discussed this before, and It's the idea of UNCHANGING sites that are unrealistic - for mining, at least. (I'm in full agreement with you all on wood collection)
From the Mining FAQ
One of the things that is constantly argued by those who have no idea how mining works in real life, is that "ore locations don't change in real life."
Perhaps they don't, exactly - but what qualifies as one man's copper ore (or even the TAILINGS left behind) is often someone else's gold or silver ore. It all depends on market value of the metals in question, at the time. Nearly every ore that exists for any metal, is ALSO a source for at least one other metal; it's just that one of the metals (sometimes two of them) are significantly more profitable to mine than the others.
From a subscription-only (free) newsgroup I read (The Baen's Bar forum, for the authors and fans of Baen Books), where the discussion of metals for investing came up, and turned to actual reclaimation of metals from ore....
Poster 1:
"Silver mining is great because most silver is not mined--it's a byproduct of zinc, copper or lead mining. Silver is an industrial metal that gets consumed. Current projects include going through the TAILINGS of older mines to scavenge what they missed, quite cost effectively, and cutting into hills to retrieve new stuff. "
Poster 2:
"Friend of mine just bought six hundred metric tons of
tailings from a Montana (copper) mine and in two weeks of processing they've recovered six hundred ounces of gold, two tons of silver, several kilos of rare earths (why those are measured in metrics I dunno) as well as lots of gem stones that in the area between rare/common. They've hardly even started into the stuff they bought from the two mines and they've already doubled their investment, paid off the processing fees for the rest of the tailings and the environmental tax to process the tailings back into reuseable earth (and if it passes EPA testing they get that tax back plus a multiplier as a deduction against their profits so it's well worth the trouble.) "
***
In these cases, these are getting multiple types of valuable metals from the LEFTOVERS of a copper mine. In fact, if the copper mine had been rich enough in gold or silver, they would have been called a mine for THOSE metals, and the COPPER would be what was left in the tailings (as was the case in the Old West (US) prior to the use of electricity causing copper to become valuable).
So, really, getting multiple metals from a single spot, over time, is not unrealistic at all - it was just implemented poorly, in terms of the change times (after all, even at 12 UO days per real day, the desirable ore of a spot changes too often to reflect what would cause you to concentrate one one metal type over another).