The OP's topic was centered around the longevity of only a 'coin'. I feel fairly certain that the intention was geared towards numismatic coins having dates even though some of the ancient coins lack dates making it even more difficult to ascertain mintage time frames.
To state the obvious the following is Webster's definition of a 'coin':
Full Definition of COIN:
1
archaic
a : corner, cornerstone, quoin
b : wedge
2
a : a usually flat piece of metal issued by governmental authority as money
b : metal money
c : something resembling a coin especially in shape
3
: something used as if it were money (as in verbal or intellectual exchange) <perhaps wisecracks . are respectable literary coin in the United States — Times Literary Supplement> <would repay him with the full coin of his mind — Ian Fleming>
4
: something having two different and usually opposing sides —usually used in the phrase the other side of the coin
5
: money <I'm in it for the coin — Sinclair Lewis>........
I put this up only to drill down upon one of the most important criteria absent from the above description that most 'accurately' denotes the scale of any coin's longevity: the date. It provides a point of reference in time.
As an example, I personally feel that the
Buffalo nickel's design taught the mint the futility of arranging the placement of the date too high above the field. Even a dateless Buffalo with excellent detail is otherwise essentially worthless.
The point of my narrative is that most if not all 'numismatic' coins use a legible date to denote the durability over time.
The bottom line is that virtually any discussion within CCF about the longevity of modern and classic coins depends upon the presence of a legible date. Without it, the process and analyses are analogous to stepping upward on a downward-going escalator creating an exercise in futility etc.