I think I encountered my 1st "expired" occurrence with my pool testing reagents.
I recently checked my pH with Taylor R-0014 (.75 Oz) that I had been using for a long time. The pH sample turned bright red, a color that I'd not seen since I began testing my pool chemicals myself in 2012.
Since I never have seen my pH lower than 7.3 in the pool (it's only that low after adding acid to lower a higher reading), I suspected the R-0014 had reached its shelf life expiration.
I tested the TA reading (Total Al) and it was 80-90 .
I tested the sample again using a pH reagent from my OTO kit, a Pentair-brand reagent. The color was normal for a 7.8 reading (light violet color).
I ordered a replacement R-0014 reagent and received it the other day. After reading this thread, I saw the expiration date on the bottle. The date shows an expiration date about 2 years in the future.
I tested pH using the new R-0014 and all appears ok although I had added Muriatic Acid to lower the pH back to 7.5 so the color is the normal neutral 7.5 color at present using the new R-0014 .
The old R-0014 didn't display any discoloration or fluid sticking to the bottle interior surface. All of my pool testing items are stored at room temp away from sunlight in a dry location.
After reading this thread, I'll label my testing items on the date
I receive them to have a reference of the shelf lives for the items.