“You have less time than you think,” I tell entrepreneurs.

From the time I was a kid, I’ve been obsessed with age and mortality. Unlike most of my peers, I was convinced that childhood was going to be the best, most carefree years of my life, and I remember thinking at age 11, “Well, at least I had a good run.”

I’ve had some pretty good years since then, but my obsession with time remains, which means I’ve thought pretty carefully about the entrepreneurial career.

You see, most of us think something along these lines:

“Retirement is a joke, and Social Security is a punchline that will never come. Forget 65, I’ll probably still be working at 75.”

As a result, we view our careers as starting in our 20s, growing in our 30s and 40s, peaking in our 50s, and slowing winding down after that. This might be true of traditional careers, but it isn’t true for entrepreneurs.

The scary thing is, if you’re an entrepreneur, your days of starting companies from scratch are probably over by age 45.

I’m not happy about this; in fact, that particular deadline will loom in my career all too soon. But it’s based on a realistic assessment of the Silicon Valley ecosystem.

Like it or not, the startup world is full of a pervasive and unacknowledged ageism. I’ll spend more time on that topic in a later post, but I’ll provide three telling data points:

1) At my recent Reverse Demo Day, one of the entrepreneurs in the audience asked the question, “How do you feel about older entrepreneurs?” The answer he got from an angel was, “We love older entrepreneurs. Some of our best entrepreneurs are in their 30s.” And he wasn’t kidding.

2) A recent article about Splunk’s IPO focused on the extreme age of its venerable CEO, Godfrey Sullivan. “Splunk CEO Twice Zuckerberg’s Age,” the headline screams. The entire focus of the article is on his anomalous age…58. One of his (younger) friends comments, ““You’d think he was 35, taking his company public. He is so energetic after all he’s done in his career.” In other words, we should be shocked that he’s vibrant rather than doddering.

3) In this great post from Adioso founder Tom Howard, he writes: “It was now my 34th birthday. I was already on the old side for a startup founder. Wait till 37 or 38 then start something new? That was no age to be starting again.”

One some level, I always knew this. I’d worked with a number of CEOs in their 50s during my career, and almost all of them saw the gig as their last before retirement. But what ratcheted up my fear to the next level was this realization:

If you wait until your mid-50s to make the transition to venture capitalist, you’re probably too late.

Like many entrepreneurs, I always viewed venture capital as the appropriate retirement plan. It’s prestigious, reasonably lucrative, and most importantly, fun. The problem is, if you want to join a VC fund as a General Partner, you need to convince your fellow partners (and even more importantly, LPs) that you’ll be going strong for the entire 10+ year life of the fund. Not many folks are willing to take a chance on newly minting a GP at age 55.

Sure, we’re surrounded by VC legends who are well past that age (think Don Valentine, Dick Kramlich, and Bill Draper, among others), but none of them started after the age of 55.

Unless you’ve hit a home run with one of your startups (which, incidentally, eliminates the need to worry about money again), you’d better start that VC transition before you turn 50.

And that means that you’d better not start a company (which is generally at least a 5-year commitment) after you turn 45.

Scary? Yes. Discouraging? Yes. But not as discouraging as discovering too late that you’ve missed your chance.

Samuel Johnson was reported to have said, “Depend upon it, sir, when a man knows he is to be hanged in a fortnight, it concentrates his mind wonderfully.”

I’ve told you when your career will hang. It’s probably sooner than you thought. Concentrate your mind, and make the most of the time you have left.

Chris Yeh

May 11, 2012