Tail insurance

We are selling a park and the buyer’s attorney put a clause in the contract requiring us to purchase tail insurance to cover any issues while we owned the park, and they want the insurance to be vaild for the duration of the statute of limitations of the potential tort or legal issue. Have any of you experienced this as a buyer or a seller? I already have a question in to Kurt Kelly - just checking to see if this is a reasonable request.

Bret