There is not actually an age at which a child is allowed to choose which parent to live with. A parent may file a motion to allow the child to testify in a time-sharing modification case. The judge will determine (on a case-by-case) whether or not to allow the child to testify as to a preference of where to live. Even if the child is allowed to testify, their preference is only one of many factors that a court will consider when making a determination of what time-sharing schedule is in the child's best interests.
Look up Florida Statue 61.13. There's a section that lists factors in determining the best interest of the child in regards to timesharing. The child's preference is listed as a factor, but not the only factor. You would most likely want to submit a petition to modify the timesharing schedule, and include some of the factors enumerated in the Statute.
Best of luck to you and your family.
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Some judges are very liberal about letting children testify, others are hesitant to let a 17-year-old testify. That is one of the advantages of having an attorney who may have had experience in the past with this particular judge. Good luck.