Is it permissible for a woman to travel far from her husband for a period exceeding four months?

If the spouses agree to this, there is no harm in it, unless the distance between them leads to a forbidden شرعي consequence, such as falling into sin or neglecting the children. In such cases, this separation is not permissible, due to the Prophet’s (peace be upon him) saying: "There should be neither harm nor reciprocal harm."