Final answer:
An agent's strategy to retain an existing life insurance policy and prevent its replacement by another policy is called conservation. This effort helps insurance companies maintain their client base and could be more advantageous than signing up new customers.
Step-by-step explanation:
An agent's attempt to stop the replacement of an existing life insurance policy is known as conservation. Conservation in this context means the agent is working to retain the policyholder's business by discouraging them from replacing their current policy with a new one. It could be motivated by the understanding that keeping an existing customer is often more beneficial for the insurance company than signing up a new one, especially if the replacement policy is with a competing insurance firm.