I was divorced over 6 months ago. How long do I have to keep her property?

Start by looking at agreement. If it's not addressed, then you need to make sure you notify her and give her a reasonable opportunity to retrieve her belongings. I would suggest that you hire an attorney to write a letter to her notifying her of deadline to retrieve belongings.

Assuming your attorney properly drafted your agreement, the answer is right there. Call him or her.

Does your settlement agreement and/or final decree address personal property at all? If not, then you need to discuss your options with an attorney, who can give you advice.

It sounds like you did the divorce yourself. Otherwise, any decent attorney would have addressed this issue by now. I wish the people who sell forms could be prosecuted for the unauthorized practice of law. This is why people shouldn't represent themselves, and NO FORM addresses every issue in every case because all cases are unique.