Chicco's manual for the Chicco KidFit gives no number of years. It tells you to stop at the "Do Not Use After" date on the seat's label.
What the maker says:
DO NOT use this Booster Seat beyond the 'Do Not Use After' date (manual gives no year count)
Source: www.chiccousa.com, checked 2026-10-24.
Look up another model, or work out the date from a manufacture date