You should get supplemental life insurance when you realize your family’s financial needs may outsize your current policy’s benefits after you pass. There’s no need to cancel your current life insurance policy and buy another one when you can get a supplemental plan to add an extra layer of protection to cover your family’s financial needs after you die.
You should also consider purchasing a supplemental policy if you need extra coverage for a spouse or child. The most cost effective time time to buy supplemental coverage is when you are in your 20s and coverage is at its cheapest.