Use the --timeout flag to change the timeout.
--timeout
herbie shell --seed 2019088 +o rules:numerics (FPCore (x) :name "3frac (problem 3.3.3)" :herbie-target (/ 2 (* x (- (* x x) 1))) (+ (- (/ 1 (+ x 1)) (/ 2 x)) (/ 1 (- x 1))))