at the edge of your seat for long stretches 
(ROOT (S (PP (IN at) (NP (NP (DT the) (NN edge)) (PP (IN of) (NP (PRP$ your) (NN seat))))) (PP (IN for) (NP (JJ long) (NNS stretches)))))
(ROOT (S (PP (IN ) (NP (NP (DT ) (NN )) (PP (IN ) (NP (PRP$ ) (NN ))))) (PP (IN ) (NP (JJ ) (NNS )))))