A glacier or a mountain does change over time but for a human’s lifespan it is usually minor. The newly established route may shift as weather, rock fall and numerous other issues impact the region but short of a major event—landslide, glacier disappearing—the route with its unique characteristics can usually be repeated. With the original route beta a subsequent attempt is often easier.
Can the same be applied to water ice? Annual water ice has a very temporal aspect even for us humans as it disappears only to be born anew the next season. So is a first ascent of a seasonal waterfall really only a first ascent for that season? Does a first ascent even matter for WI climbs?
Cheers!