
Evanescent
Quick Disappearance
Use 'evanescent' to describe something that fades out or ends rapidly, not just physically but perhaps in memory or importance. 
Seldom Negative
'Evanescent' often has a neutral or slightly positive connotation, not usually used in a negative context. 
Poetic Expression
'Evanescent' is popular in literary or poetic contexts for its descriptive elegance. 