"It's surreal," says Seacrest, whose last chapter on Idol is featured in the current issue of PEOPLE.
Reading a goodbye note from a crew member he has worked with since the reality singing competition began in 2002 – when his life was forever changed – Seacrest accepts the inevitable.
"It's starting to sink in," he explains. "But I don't think it will really hit me until I say, 'Goodnight, America,' that one last time."
"Goodbye" is something the Idol team has been saying a lot lately. They won't really part ways until after the epic series finale – which will air live from the nearby Dolby Theater on Thursday – but a few weeks earlier Seacrest got the crew of approximately 300 together to celebrate the end of an era.
"I took them out as a thank you," he says. "It was great."
For more from Seacrest – including what his hardest day of hosting was – pick up the latest issue of PEOPLE, on newsstands Friday.
The ever-busy Seacrest is jumping into other gigs (he'll continue to host his radio shows and New Year's Rockin' Eve as well as the late-night hour of NBC's Olympics coverage), but that doesn't mean he'll soon forget his time spent on Idol.
For more on Idol, pick up PEOPLE's The Best of American Idol collector's edition issue, on sale now.
"I have plans to raid our storage garage for some signs and mementos," he admits. "I want things I can keep in my basement forever."
The American Idol series finale airs Thursday at 8 p.m. ET on Fox.