According to everything I've ever been told by people more knowledgeable than me, is that 2 piece golf balls stored at room temperature have virtually no expiration and no effect on performance that was designed at the time of manufacture.

Solid core balls not frozen/not baked/not stored in a hazard may not have a time limit - it is likely longer than 4-5 years. The one variable is the changing construction. A Pro-V1 392 will play differently than a 2019 release. Different core material, different material in the cover, and adjustments to the dimple pattern. The rubber wrappings in balls prior to the V line can deteriorate.

These guys are spot on. My body is deteriorating faster than my ProV1x's. Not really a science project I want to do, to see which one gives out first.

It's always nice to read that the balls I have in my "golf closet" will not spoil. If I have about 240 balls and I lose 3 per round I have enough for the next 80 rounds. That doesn't even figure in my finding other balls while in search of mine. I'm glad I don't have to worry about those balls failing me...

Really good question and good discussion. I have always kept them inside in a closet but always had this thought to myself and never asked. Thanks for sharing the knowledge everyone!