Our study assessed the relationship between the duration of venovenous extracorporeal membrane oxygenation (V-V ECMO) and patient outcomes. We studied patients undergoing V-V ECMO support for acute respiratory distress syndrome (ARDS) between 2009 and 2017 who were reported to the Extracorporeal Life Support Organization registry. We evaluated survival, major bleeding, renal failure, pulmonary complications, mechanical complications, neurologic complications, infection, and duration of V-V ECMO support. Multivariable regression modeling assessed risk factors for adverse events. Of the 4,636 patients studied, the mean support duration was 12.2 ± 13.7 days. There was a progressive increase in survival after the initiation of V-VECMO, peaking at a survival rate of 73% at 10 days of support. However, a single-day increase in V-V ECMO duration was associated with increased bleeding events (odds ratio [OR] 1.038; 95% confidence interval [CI]: 1.029–1.047; p < 0.0001), renal failure (OR 1.018; 95% CI: 1.010–1.027; p < 0.0001), mechanical complications (OR 1.065; 95% CI: 1.053–1.076; p < 0.0001), pulmonary complications (OR 1.04; 95% CI: 1.03–1.05; p < 0.0001), and infection (OR 1.04; 95% CI: 1.03–1.05; p < 0.0001). V-V ECMO progressively increases survival for ARDS over the first 10 days of support. Thereafter, rising complications associated with prolonged durations of support result in a progressive decline in survival.