Copper, Iron etc. mines

Why bother upgrading a copper or an iron mine or even a well, when I have to start from lvl 1 again when they collapse?

So that you accumilate resources fast enough to supply your hungry producers. There are a limit to the amount of mines you can find.

There is not much point in upgrading mines, but keep one upgraded gold- and one ironmine for refills from adventures.

Thanks both of you guys; I'm about to get to lvl 21 and as long as I get free gems every now and then, I would be able to buy some of those so called "iron diviners" and "golden parrots".
I'm not spending a dime for them....