They are past their shelf life. Send them to me and I will properly dispose of them for you. ☺

If they have been kept inside (in a closet or basement) and not exposed to extreme heat or cold, they are probably still okay. You may have some distance loss with them, but not to much.

Various sites like Golfwrx suggest 5 years. If stored in an even temperature like a basement, they are likely ok, although 3 versions back. That is as much a factor as age if you switch between those and the current version. My garage varies from -10 to 95+ throughout the year. I'd expect 6 year old balls to be past their prime if I kept them there.

I have a similar question. The other day while playing one of my partners hit his ball into an area that has recently been under construction and the ground there was very soft for a period of time when the improvements were made. The ground now is very firm but it was a gold mine for lost golf balls. There were literally dozens of balls buried with just their top surfaces barely showing. I dug up a half dozen ProV1's and cleaned them up and they look brand new. Would these balls lose any of their performance ?

They will probably make good shag balls.

Good info. Thanks

I have used pro v's separated in boxes by year, that are older than 6 years and they still work well. The ones you have that were never used , should be just fine!