Record of successful being on ECMO

V/V ECMO

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5474617/ case of 300+ days on ECMO V/V
https://pubmed.ncbi.nlm.nih.gov/19896387/ 2010y - case of 107 days on ECMO V/V (survived for 351 days post-transplantation). "The total length of ECMO support of 107 days required replacement of 48 oxygenators, 21 pump heads and three cannullae". Before that case they say the record was 57 days.
https://pubmed.ncbi.nlm.nih.gov/26029505/ - "ECMO was maintained for 36 days" that's VV ECMO

A/V ECMO

https://pubmed.ncbi.nlm.nih.gov/28264702/ 87 days. "In total, 2699 runs over 14,747 days of VA ECMO were analysed <...> The duration of ECMO support varied (0–87 days), with a long tail of long-term support: 75% of patients were supported for less than 1 week and 96% were supported for less than 3 weeks". Though not sure how successful that case with 87 days was.
Though if they mean this case[1] there 87 days were composed of 26 days on VA ECMO and 61 days on VV ECMO.

https://pubmed.ncbi.nlm.nih.gov/18675627/ - "we describe the first 2 reported cases of children with adenoviral pneumonia who survived after more than 30 days of ECMO support".
Case 1: "36 total days on ECMO", "On HD no. 7, the patient was placed on venoarterial (VA) ECMO <...> "On HD no. 19, the patient was briefly trialed off ECMO but failed conventional management and was placed back on venovenous (VV) support after less than 48 hrs"
case 2 - 37 days on A/V ECMO (seems)
though fig.1 shows that survival in adenoviral is much less than in other infections so need to search more