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.
Imprudence redirects here. For the French short story, see Imprudence (Maupassant short story). Prudence (Latin: prudentia, contracted from providentia meaning seeing ahead, sagacity) is the ability to govern and discipline oneself by the use of reason. It is classically considered to be a virtue, and in particular one of the four Cardinal virtues (which are, with the three theological virtues, part of the seven virtues).