Answer: longest

AnswerCrossword Clue
LONGEST

Most enduring

LONGEST

Most likely to put you to sleep?

LONGEST

Extended to the max

LONGEST
Most tedious
LONGEST
Guinness superlative
LONGESTTops in endurance
LONGESTWhat "antidisestablishmentarianism" is.
LONGESTMost extended.
LONGESTMost protracted
LONGESTOf greatest duration
LONGESTMost time-consuming
LONGESTMost extensive
LONGESTMost extended
LONGESTLike the day of the summer solstice
LONGESTLike the papacy of Pius IX, after St. Peter
LONGESTBilly Joel "The ... Time"
LONGEST"The ..... Day" (1962)
LONGESTType of yard in a Burt Reynolds flick