Well, they DO run out, DH, it's just that they do so so rarely and in such an arbitrary fashion.
Resources is another area which should DEFINITELY be retained, but also needs much better fine tuning. This is how I would improve resources:
1) Add the ability to 'prospect' for resources. Prospecting should cost city resources, but increase the 'probability' of a resource appearing in a square.
Obviously what, if anything, turns up would depend on factors of rarity, terrain and tech level.
2) Using prospecting it should be possible, if unlikely, to discover a resource before you have the tech to make use of it. This is not unrealistic as some resources-like Oil-were known of LONG before the ability to refine and distill it became available.
3) Resources should have a 'size' rating-this effects the disappearance ratio.
4) The chance of a resource vanishing would depend on a) 'scarcity', b) 'rarity', c) resource 'size', d) '# and size of cities in the civ', e) number of resource 'units' currently traded, f) # of units/improvements being built-that turn-that have the resource as a PR (like iron for swordsmen), g) the number of units/improvements already built that have the resource as an 'ongoing requirement'.
5) Certain resources, if in a tile currently being exploited, should cause pollution!
If these alterations to the resource model were made, I think that it would be absolutely PERFECT!!
Yours,
Aussie_Lurker.
