decadelong

or dec·ade-long

[ dek-eyd-lawng; British also duh-keyd-lawng ]
/ ˈdɛk eɪdˌlɔŋ; British also dəˈkeɪd lɔŋ /

adjective

lasting for a decade: After a decadelong study, the drug has finally been approved by the FDA.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for decade-long