Q: Someone entrusted me with a crate of books for a week. If he did not pick it up at the end of the week, do I remain responsible for it?

A: A guardian remains responsible for the entrusted item until it is returned safely to the owner (see C.M. 293:4; Pischei Choshen, Pikadon 7:2). However, if he explicitly told the owner that he does not want to watch anymore, he is no longer liable, even for negligence (Rema 74:3; Sm”a 120:11).

Machaneh Ephraim argues, though, that if he accepted responsibility for a set time, he is not liable after that time (see, however, Aruch Hashulchan 291:20). A shomer sachar, after the designated time, reverts to a shomer chinam (304:6; 343:2).

A bookbinder is considered a shomer sachar on the books he is binding, but when he finishes his work, he reverts to a shomer chinam - unless he insists on payment before returning the books. If he explicitly tells the owner to pick up the books and that he does not want to be the shomer after the set time, he is not responsible according to most authorities (306:1; P.C., Pikadon 7:9).

A shoel (borrower) who borrowed books reverts to a shomer sachar after the set time (343:1).