If you're not successful (in worldly terms, I'm talking a comfortable level of wealth etc) by the time you're in your 40s, is it too late?
Yes, for most people, its too late. While there are a few who are physically fit enough and have the genetics to meet the burden of the workload, for most of us, its too much.
That's a very general statement however and only applies to the largest majority of success paths.
Here are some comments.. sort of classifications of these paths to success..
Intellectual Means to Success:
Those who obtain success through intellectual means usually do it by learning something unique or in high demand in their 20's and 30's.. Professionals like doctors and lawyers and engineers. By the time a human reaches 40, the creation of new neural pathways within the brain has slowed to only a small fraction of what it was during our younger years.. You can forget about learning anything ground shaking new. Almost everyone has heard the phrase "You can't teach an old dog new tricks".. this is exactly what it means.
Entrepreneurial Success: (this was mine).
Any normal business that is going to make you successful isn't going to be easy. People who open tanning salons or hot dog stands don't make much money. To open a meaningful business and turn it into a money making engine, takes several years worth of 80 to 100 hour work weeks. Interestingly, the longer the duration required to mature the business, the more profitable and stable they usually are. Businesses like restaurants can usually mature within two or three years but they're not usually very stable or lucrative. Manufacturing facilities (my area) can take up to 10 - 15 years to mature, but when they do, they are usually rock solid stable and provide a nice income.
The point is that when you've reached your 40's, most of us no longer possess the youthful energy required to put in the long work hours required without some type of medical consequences. I used to work 16 to 18 hours a day and would sometimes fall asleep next to a piece of machinery only to be found the next morning.. Usually by an employee trying to wake me up with a cup of coffee. I couldn't hold that pace today if my life depended on it.
Inventing Something:
Even in your 40's this one still holds much promise. Inventing something and carrying it to market is one of those area's where age actually provides some advantage.. The drawback is that most don't have the intellectual horsepower to invent anything meaningful or they just don't run across that magic spark that brings the idea to them. Its a very "hit-and-miss" type of thing and not something anyone can count on.
Cheap, Massless, and Lacking Substance:
This category describes everything that has little physical value or real world usefulness but which can be marketed to the masses for a pretty penny. Writing a book that has a good story.. Most folks don't know that when Sylvester Stallone wrote the first Rocky movie that he only had about $300 in left in his bank account. The movie studio wanted someone else to play the part but he was prepared to walk away if it wasn't him. Anyone of any age can write a book and if your story is clever, you can make a lot of money.
Other things in this category include re-branding and relabeling existing products for new applications, insightful investments (kind of far fetched), and most entertainment related successes..
Conclusion:
For the most part, once you reach your 40's, your chances of financial success take a nose dive. But that doesn't mean you can't find other ways of being successful. Many folks don't measure success by monetary means.. their measuring stick is based on family and friends and relationships. Others base their success on personal goals or other things that have little to do with financial numbers.
It is said that money doesn't buy happiness and that statement is true for the most part. I have friends who's wealth is in the high 7 figures and I wouldn't want to live my life in their shoes even with all that money.. and I have another friend who barely clears $40K/year and I can tell you that when he dies, you won't want to be caught at the traffic light when his funeral procession drives by because it will probably be 4 miles long.
Good luck,,,