Pinterest, Snapchat, Uber. These Silicon Valley tech companies have collectively raked in billions of dollars of investor cash and recorded jaw-dropping valuations in recent years. What else do they have in common? They're eschewing the traditional exit strategies customary among startups--which are, going public or getting acquired.   

Yet evidence is mounting that this strategy may soon backfire. So far this year, more cash was seen going into tech companies than what's coming out by way of exits, according to a study released on Thursday by venture capital researcher CB Insights. One interpretation of this report is less than optimistic--that is, more money may be chasing the next hot tech companies than is realistic. And that raises yet more concerns about the possiblity of a bubble in tech firms. The reason is, at some point, investors may wise up to the fact that they may not be able to recoup their investment--much less the see returns they expected.

So if you have a small tech company that you're hoping will get acquired, or even go public in the next couple of years, the trend bears watching so you can keep tabs on your own valuation. While you, of course, want as high a price tag as possible for your business, it’s important to be realistic about your exit plans. If your valuation is too high, it may interfere with your plans to sell or go public. And that’s particularly important, in an era where realistic valuations have seemingly been thrown out the window.

Year to date for 2015, investors poured $42 billion into tech companies, but exits, which include either initial public offerings, or mergers and acquisitions were only worth $26 billion, CB reports. The reduced exit dollars reverses a trend over the last five years, where exits have been worth between two and eight times the annual amount of investor money flowing into tech companies. In 2012, for example, venture capital and private equity firms invested $18.5 billion into tech companies, and exits for such companies were worth a staggering $149 billion.

It used to be that tech companies went public sooner and with much lower valuations. Amazon, for example, went public two years after its series A round of $8 million Kleiner Perkins Caufield and Byers, at a valuation of about $440 million. By contrast, Facebook famously went public in 2012 at a valuation of $104 billion, though seven years after its Series A. And one need look no further than Uber, which has pulled in more than $8 billion in funding is now worth a staggering $50 billion. It remains private six years after its launch.

And for tech companies that did test the exit waters, certainly their market performance in 2015 suggests they may have gotten higher valuations than they deserved.

Cloud storage company Box, an Inc. 5000 company, went public in January, at a pre-IPO valuation of around $2.4 billion. By the time Box went public, however, its valuation had dropped more than $700 million to $1.7 billion, with shares pricing on the low end, at $14. Although the company’s price per share popped to $25 soon after its IPO, shares have fallen by half since then, and are currently trading at around $12. Its market cap is now $1.5 billion.

Once high-flying Twitter is another example. The current value of its shares outstanding is $21 billion, about 20 percent lower than its immediate post-IPO market cap in November 2013.

Certainly it may still be tempting to hold off selling or going public until you get the highest valuation you can secure. But common sense says if you’re in it for the long haul, make sure you’re profitable, and offer a product or service whose worth is not a mirage.

“This trend is driven by companies staying private longer and raising mega-rounds in private markets, yielding companies that have raised sizable war-chests with valuations that are only validated on paper,” CB Insights said in its report.