Crypto owners got a much-needed reprieve on Wednesday with bitcoin and major digital currencies posting double-digit gains, breathing life into their portfolios that have been shredded to pieces of late.

However, venture capital guru Fred Wilson said those dabbling in cryptocurrencies should enjoy the rally while it lasts.

In a recent blog post titled “what bear markets look like,” the co-founder of Union Square Ventures said the hard times for digital currency owners are far from over. Drawing comparison with Amazon AMZN, +2.49% and the dot-com bubble of the late 1990s and early 2000s, Wilson said the lofty heights of late 2017 for bitcoin and other digital currencies could be years away.

“Amazon peaked in the Internet bubble in late 1999 at around $90/share. Almost two years later, at the trough, you could briefly buy Amazon at $6/share,” he wrote. “And then it took until late 2007 for Amazon to trade above the highs it reached in 1999.”

“So while crypto asset prices are down 80-95% in USD terms over the last year, they could and probably will go lower,” he continued.

Read:Bitcoin is on track to do something it hasn’t done in 4 years

And if you’re wondering how credentialed Wilson is, this is what he said in a Jan. 7 post when a single bitcoin was fetching more than $17,000.

“ ‘If you are sitting on 20x, 50x, 100x your money on a crypto investment, it would not be a mistake to sell 10%, 20% or even 30% of your position’ ” — Fred Wilson on Jan. 7, 2018

Since his call, bitcoin BTCUSD, -0.00% is down more than 75% and the total value of all cryptocurrencies has plummeted more than $700 billion.

Read:Bitcoin is imploding — here’s where bitcoin bulls and bears see it headed from here

Yet, despite his cautious remarks, Wilson is a true crypto evangelist. The early adopter and bitcoin bug has made multiple investments in blockchain-based projects, and in June he said 15% of his active portfolio is made up of companies in the crypto and blockchain sector.

Despite his comments, Wilson said those willing to ride out the storm could be banking some fat profits in years to come—but not before a few more hiccups. “I think some crypto asset (and possibly a number of crypto assets) will have a price chart like Amazon’s current one in 18 years,” he said.

“But we will have to do what Amazon did, hunker down and build value and survive, for quite a while to get there. And I think things will get worse before they get better.”