Merry Christmas and Happy Holidays to you all! (Especially Brad Klein and all the New Yorkers this year)
I have a bit of time after gift opening and before the big feast, and have been pondering this thread.
I tend to disagree with my friend Jeff McDowell on this one. I have always felt you need about a decade of experience (read mistakes) under your belt to do your best work, regardless of passion. I can only base it on my own experience, of course, but a lot of factors go into making the right decisions, and making the wrong ones a few times is almost a must to really learn the craft.
I went on my own after seven good learning years at a good firm. I didn't feel I knew it all at that time, but that I would learn faster by making mistakes on my own name and money. My first seven years on my own were spent doing mostly lower budget projects, and thinking mostly from a cost only perspective, whch, for example, kept me from doing big greens (smaller ones are cheaper).
Obviously, I did enough right to start getting some bigger projects on better sites, but it took some time to develop the style and mannerisms to say no to many negative influences that you usually don't have when younger. (Poor contactors, Good Contractors who test your resolve, Owner's with low budgets that could be raised if only you hit the right buttons, etc.)
Also, when first on my own, I felt the need to change styles from my predesessors (as if they were my only competition (duh!)) and went through a few gyrations in the evolution of my style. I have also been lucky to study more of the great courses old and new in the last dozen years. While all that study may have been done at a very early age by a select few, that most architects don't get that chance. It also doesn't hurt to have lots of alone time on planes and in hotels to really do some doodles and creative conceptual thinking on golf design, either!
The practical side of things is most architects have to "learn on the job" to apply those conceptual thoughts technically to an individual site. Well, there may be smarter guys than me, but true learning - about the conceptual, techical and business sides of the profession usually comes slowly, and you can always learn more with more time, and all are important to doing good work. So, most architects, IMHO, do get better with age,
I agree with Jeff that passion is important, so there is no reason not to keep getting better with age, providing health allows and the passion stay with us. Sadly, there have been some for whom this is not true (including CB Mac and Tillie, among others)