People need money in their 20s and 30s , when they are building their lifes. Buy a new house, pay school for kids, etc... At 60s-70s money isn't so important anymore, so it is not a good time to receive heritage.
The trouble with bequeathing money to people in their 20s is that far too often it gets wasted on things like cars, clothing, restaurant meals, etc.
It's much better to wait until they're 40 when they're entering the prime of their lives and are more likely to use the money wisely. Most people are grown up by the time they reach their 40s. By then they've probably learned the value of work and thriftiness.
Some people recommend to give 1/3 at age 30, 1/3 at 35 and 1/3 at 40 or 1/2 at 30 and 1/2 at 40.
Giving money to someone when they are 60 years old is not optimal, imho, but I agree about early-mid twenties.