Transitions in time...

I'm wondering if there's some sort of theorem that correlates the number of major life transitions within a given timeframe to stress or some other reaction.

Let's say, for example, that my grandfather is right and that the three biggest decisions in a person's life are:
1. whom to marry
2. when to have your 1st child
3. when to buy your first house

Some people do all of this within 1 year others never do all of them.

In going through the normal trials and tribulations of life the other day, I was just struck by the fact that just over 5 years ago, I had made none of these decisions. Now, I've made all of them.