Photopolymer Plate Longevity

I’m wondering, if stored properly, how long one can expect photopolymer plates to last/still print well? If they don’t have any noticeable cracks, bends or defects, is there something inherent in the plastic that will degrade the image over time? I’m asking because I recently noticed on Boxcar’s site that they say their plates should last for a year. This surprised me because I’m still printing with some plates that are quite a bit older than that. I do short runs, so probably none of my plates have been used for more than 1,000 impressions at most. I do sometimes have less than stellar printing results, but had been blaming that on my lack of expertise, or on the ink used that day (some of that is pretty old too), or arrangement of the planets, etc. So just would like to know from those of you who use photopolymer what your opinions are on this. Thank you!

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I have some metal backed polymer plates still mounted that are 30 years old at least. Recently I put a 4page down on to honey combe mount and printed them on my Miehle Vertical and they were as good as the day they were made. The only problem that occurred was a corner of the double sided tape had dried out. Aluminium backed plates are almost imposible to lift and re-lay. These plates I have are almost certainly the old alcohol developed type. Picture shows 3 30 year old polymers with a space where one was lifted

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I am also newish to printing with polymer, but I’ve noticed that the plates I have that have just a few thin lines have been holding up much better than ones with big solid areas, which curl up quickly.

I recently noticed that expiration date on the Boxcar site as well! I actually asked about it because I was pondering how much unexposed plate material to buy. And that’s the thing..I’ve had good experiences making plates from unexposed material that was definitely older than a year! So in regards to unexposed stuff (again with proper care and storage)..plate material lasts awhile!

As for already made plates, I feel pretty confident they last longer than a year but I’m not sure in what ways they might break down over time.

I mount polymer plates on MDF or 3/4” plywood. I find that most plates will last many years although they may roll up in which case I just clean and remount them and they continue to print well. There are many polymer plates here that are 5 or 10 years old from before my time here. Most of these plates were made at various outside shops from variously colored polymer materials but mostly they print well. Some have been nicked or smashed. Smashing a polymer plate a little too hard can result in a discoloration that eventually breaks and cracks off. Sometimes a plate will get soft and sticky or melt. I believe that light and humidity will tend to degrade them that way but it’s also possible that they were improperly made in the first place and didn’t get the second hardening exposure after they were developed.
So for me if a plate is made well and taken care of they can last many years.