decades-long

adjective
de·​cades-long | \ How to pronounce decades-long (audio) \
variants: or less commonly decadeslong

Definition of decades-long

: lasting two or more decades : occurring over a period of two or more decades … no discussion of wolf research would be complete without mention of this fascinating, decades-long study.— Robert R. Ream His decades-long accumulation of books makes an eclectic mix …— Stephen Mihm

First Known Use of decades-long

1930, in the meaning defined above

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