Use the --timeout flag to change the timeout.
herbie shell --seed 2020322
(FPCore (x l t)
:name "Toniolo and Linder, Equation (7)"
:precision binary64
(/ (* (sqrt 2.0) t) (sqrt (- (* (/ (+ x 1.0) (- x 1.0)) (+ (* l l) (* 2.0 (* t t)))) (* l l)))))