What should one do, if one isn’t sure (due to inadvertence/mistakes in storing it) whether pesachdike dishes/cutlery are milchig or fleishig? Is there something like a ‘jud-beis choidesh’ concept to rely on? – Gutn moed!
Under the circumstances the best advice is to perform hag’alah – immersing in boiling water – and this will help for using the utensil anew.
It is true that the Chacham Zvi (75) and later authorities (Maharsham 2:141 and others) write that after a year the beliyos are no longer considered present, this is not relied on for using the utensils lechatchilah, but only on a bedieved level.