The insurance periods have been amended on CTC's request, which accounts for the higher cost if you have recently applied for it...
Standard periods (I believe) are 28 months for Term Life Assurance, 24 months for Bond Insurance (or until TR is achieved) and 18 months for the personal possessions / travel insurance. Kerosene mentioned the cost...around £1300 I believe.
Before they were amended, cadets were having to update / renew insurance whilst still abroad.