Chicco's manual for the Chicco KidFit Zip Plus 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