No-they do not expire. No US stamps issued since 1865 have been been devalued. The only exception are the special delivery stamps which paid for service no. longer offered. Air mail stamps are good for any purpose. Some stamps can't be used for certain things.
the pure and concentrated essence of a substance. 2. the most perfect embodiment of something. 3. (in ancient and medieval philosophy) the fifth essence or element, ether, supposed to be the constituent matter of the heavenly bodies, the others being air, fire, earth, and water. Origin of quintessence.
If someone tells you youâre the quintessential rock musician, that means they think that everything about you screams ârock and roll.â Quintessential means embodying or possessing the essence of something. Some people think that baseball is the quintessential American sport. (Others might think it's stock car racing.) We also call something quintessential if itâs absolutely necessary. A quintessential part of a lasting friendship is mutual respect.