A week from Thursday, if nothing changes, SpaceX will go public, in what is expected to be the biggest initial public offering ever. Anthropic has also filed for an IPO, likely later this year. OpenAI is moving in that direction, too.With all the hype around these companies, should retail investors — or regular people, for that matter — get in on these IPOs?When Apple went public in 1980, shares were $22. If you’d bought $1,000 worth back then and held it, you would have about $3 million today.Kathleen Hanley, a finance professor at Lehigh University, said buying and holding is generally a good investing strategy, but with these big, hyped IPOs, it might be a different story.“I think many investors think, ‘Oh, I'm going to make a huge profit off this and sell it right away,’” she said.The thing is, that often doesn’t work out for regular people — most of whom can only buy stock on the secondary market, once the price has already shot up.“For the most part, one should not expect short-run profits right after trading,” Hanley said. “We know that many of these firms underperform.” Meaning their share price declines after they go public.Remember: For all the Apples, Amazons, and Nvidias of the world, “there have also, over the years, been hundreds of other highly touted tech companies that now you never have heard of, because they haven't lived up to all of the potential,” said Jay Ritter, director of the IPO Initiative at the University of Florida.As for SpaceX, Anthropic and OpenAI? “These are great companies,” Ritter said. “A great company doesn't automatically mean it's a great investment.”When the initial valuation and stock price are so high, he said, it can take a long time to pay off.Take Apple: “It jumped on the first day of trading, about 30%,” Ritter said. And then, it largely underperformed for the next two decades.