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.
In the Summa theologiae magnificence is a virtue that belongs to God, which can also be shared by men (Summa, IIa IIae q. 134 art. 1). Aquinas adopts Ciceroâs definition of magnificence, highlighting how it consists in doing great things. Magnificence belongs to the virtue of fortitude, or courage, because it regards the undertaking of great things and actions, and persevering even when circumstances can make their realization arduous (Summa, IIa IIae q. 134 art. 1-4).