I am not sure you are required to be insured for 7 years. I think that is a strong recommendation because you have to be insured when the lawsuit occurs. The fact that you were insured when the event took place doesn't matter.
I said: "Insurer" meaning the insurance company that insures you as a dive professional.
Different subject:
One thing for sure, if you stop teaching this year, this doesn't mean that you should drop your dive instructor insurance at the end of the year too.