Die when you are young, the family needs the money. Die when you are older, you should have retirement set and don't need as much money.
Also, if what you think is a lot of money today really won't be in the future. Don't be afraid of adding to or updating your policy later on.
$500,000 today sounds like a lot. However, add a 4 kids, a mortgage and 20 years of inflation and $500,000 isn't that much.