It was something that they were in a position to do one time and no one before or no one since could ever reduplicate it.
( It ( ( ( was something ) ( that ( they ( were ( in ( a ( position ( to ( ( ( do ( ( ( one time ) and ) ( no one ) ) ) ( before ( or ( no one ) ) ) ) ( since ( ( could ever ) ( reduplicate it ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP It)) (VP (VBD was) (NP (NN something)) (SBAR (IN that) (S (NP (PRP they)) (VP (VBD were) (PP (IN in) (NP (DT a) (NN position) (S (VP (TO to) (VP (VB do) (NP (NP (CD one) (NN time)) (CC and) (NP (DT no) (NN one))) (PP (IN before) (NP (QP (CC or) (DT no) (NN one)))) (SBAR (IN since) (S (VP (MD could) (ADVP (RB ever)) (VP (VB reduplicate) (NP (PRP it))))))))))))))) (. .)))
It was a once in a lifetime thing for them.
( It ( ( was ( ( a ( ( once ( in ( a lifetime ) ) ) thing ) ) ( for them ) ) ) . ) )
(ROOT (S (NP (PRP It)) (VP (VBD was) (NP (NP (DT a) (ADJP (RB once) (PP (IN in) (NP (DT a) (NN lifetime)))) (NN thing)) (PP (IN for) (NP (PRP them))))) (. .)))