This opts _not_ to expose item "age" a la #2753 because "age" is a misleading term for it. In addition, further inspection of the problem led me to realize that exposing control of that AND despawn timeout was more complicated than simply having a despawn delay timer exactly like the pickup delay one. Everyone knows a countdown timer stops at 0, so this way we don't need any method to control the limit.
Closes#2667Closes#2753
c266f86b1b