Strip it off and put on new. You can strip off half and just replace the line you threw away. Line is cheap. I replace my line more often than most. My walleye reels get new line every couple months. Pan fish reels every month. I buy line in bulk much cheaper than the 300 yard spools you get at sporting goods store.

If it is braid just reverse it.

I fish a lot and don’t want to loose fish due to bad line.

 

UV rays from the sun are the biggest killers of mono line. Has it been kept in a dark basement ? It sounds like you're talking spools that haven't been put on a reel yet. Those can last some years if stored right. Do you have a bow scale ? Tie them on and give them a pull. See where they break at.

 

If mono, run a piece between your fingers. If it leaves a white chalky residue, pitch it. Braid will keep for a long time and so will Flourocarbon if kept in a cool place.

 

cover hands, wrap line around hands, pull

 

I've found a few bad spools doing this.

 

Line will keep a long time if kept out of the sun. Mono needs changed more often when in the sun. Braid last a long time color will fade.