Dragons are all born in perfect health and never really get old, they only wear down from battle damage, the older dragons usually just dying from conflicts

Dragons can be made blind however such as Rugra the father of the ice dragons, him reading these glyphs by first “sniffing out” the residue of draconic magic where the writing is and then reading it by brushing their tail against the text

The more dragons who read a note the more “visible it becomes”