Sorry for the lapsed time on the response to this, but attached you will find a document stating the stability of thermal paper. As you will see this is a report from a vendor and obviously all specifications must be met to achieve the desired stability of the printed paper. I hope this helps you answer your question.
Thanks to Ian Piper for researching this.
Larry J. Dix
Vice President of Operations
Global Election Systems
I believe that someone in support or product development was to let us know what thermal printer paper would be readable 22 months later, and under what conditions it would need to be stored.
Could Larry Dix or Jeff Dean please follow up with this?
Life of Thermal Paper.pdf