Irreversibility is commonly assumed to imply rapid collapse or monotonic degradation. This article challenges that assumption by introducing the concept of temporal buoyancy: a structural condition under which systems persist not through stability or equilibrium, but through saturation of accessible future alternatives. Drawing on a generalized Archimedean exclusion principle, the analysis shows that persistence can arise as a compensatory effect of constrained future spaces. The result is a non-empirical, non-ontological framework that clarifies why certain systems endure despite irreversible dynamics, and why anticipation, prediction, and control can fail even in the absence of instability.