In 2011 I got a 2003 XJR1300 that had less than 10 miles on the clock. Dude bought it new in 2005, rode it a couple times around the block and parked it in his garage under a cover. When I got it the Macadam 90X tires were like new, still shiny from whatever coating they have from new. Bike had been stored in a closed garage in Mexico City, with it's mild weather, all those years.
I ended up riding that bike from Mexico City to San Antonio on the Macadam 90s in 2012 and didn't replace them until the rear was bald. Never had an issue with those tires.
Back in 2017 I got my 2013 Daytona 675R with 5,000 miles on the clock. These things being so scarce it had to be a fly and ride, bought it in Monterrey, NL and rode it Mexico City. Monterrey is known for it's extreme weather and temperature swings, the bike had no signs of being exposed to the elements, so all the time it was parked it was under a roof, but not temperature controlled. The tires were flat spotted from being parked for so long (also squared off from straight line riding) and had little traction even though there was still some thread left. Had to take it very easy but they made the 500 miles back home; the bike vibrated like the tires were out of balance... But after removing the wheels I found out they were perfectly balanced.
All that is to say that it depends a lot on how they were stored.