If I borrow a generator from a neighbor, then I am morally obligated to return it when my immediate need for it is over  But suppose, instead, I borrow a car, and when I go to return it, the neighbor from whom I borrowed it is very drunk and wants to drive the car; then the obligation to return the car immediately is much less clear
So not all cases of borrowing are equivalent
Although having borrowed something gives rise, in an ordinary case, to an obligation to return the item promptly, it does not so obviously give rise to such an obligation in every case.