What causes tile adhesive to only have a short shelf life?

[Milleniumaire]

I have some Ultra TileFix ProFlex SPES flexible tile adhesive, which has been stored in the garage on a shelf since it was used in 2021. Even in an unopened bag it only has a shelf life of 12 months.

I have 4 cracked floor tiles I want to replace and briefly thought about using this.

What is it about tile adhesive that means it has a short shelf life?

 

[johnny2007]

I've used 10 year old open bags and worked fine.
Although, I wrap them in cling film when I need to leave them for a while.
Said that, I wouldn't use them for a "quality" job.
Ok for repairs in run down bathrooms and kitchens or small patches.