You make a valid point. Depends also what an edge is based upon.
If you know 90% of traders refuse to follow a certain tactic for
optimizing profit, then it's highly unlikely to lose that edge.
Also, imagine if one's edge is based upon the cyclic nature
of markets. If the market never ends, neither will the Cycles
that define it. Of course their phases may change,
but the same formulas/ratios are used to define the cycle.
The market is a multi-dimensional geometric solid (CYCLES within a square)
rotating on our chart screen.
Basically the same principles of physics governing
the structure of the atom and forces of energy
in cyclic action, also define the CYCLIC structure
of the markets.
Natural Law never changes, only we do.