Of utmost duration (7)
I believe the answer is:
longest
(Other definitions for longest that I've seen before include "For the most time" , "Extending farthest" , "Having the most length" , "Of greatest duration" , "Least short" .)
I believe the answer is:
longest
(Other definitions for longest that I've seen before include "For the most time" , "Extending farthest" , "Having the most length" , "Of greatest duration" , "Least short" .)