The only debt I can think of that is worth accruing is student debt and a mortgage. If you can't pay off your student debt by age 27 you've probably made the wrong career or university choice and if you can't pay your first mortgage off by 35 you've probably spent too much on your first house.
That's making a lot of assumptions about life choices.
We are on a MMM forum. Certain assumptions will be made.
I thought on MMM we didn't believe in paying off loans that are typically low-interest :)
I'm 29 and I just made my very first loan payment for undergrad this month. In my country you're allowed to defer paying it back until 7 years after you've received your last payment, which I did. I am also planning to take the full 30-year term to pay off my mortgage which means I'll not be debt free until I'm 54.
Of course, any debts people take out should be reasonable, which means I wouldn't take out more student loans than what I can expect to earn in one year or take out a mortgage that is higher than the cost of the average house in my area, and any high interest debt should be paid back asap.
Now, if we go back to mr O'Leary, while I don't agree with the details - for example, paying off a mortgage first and only start to save for retirement at age 45 once you've eliminated all other debt sounds like a stupid idea to me - I do believe that for the average non-MMM person, having at least a positive net worth by age 45 is a very good guideline. And I totally think he's right in saying that if you haven't achieved a positive net worth by then, it's going to be very difficult for you to retire at a reasonable age with a reasonable amount of money.
I also really like that the author warns about fees, which is not something that is often mentioned in articles about saving for retirement.