Car seats are made primarily of 3 materials: plastics, fabric and impact foams. The number one reason car seats are meant to be disposed of after 10 years is that those plastics and foams age and degrade especially with repeated and prolonged exposure to UV rays, extreme heat, extreme cold, etc.
Over time that degradation can make those plastics and foams extremely brittle and can limit their ability to withstand a crash safely. Think about using a plastic item for over 10 years and they have sat outside that whole time, chances are they would be weakened and nowhere near as strong as they were when brand new.
The same thing goes for the materials in a car seat. Brittle materials that can’t take an impact are NOT the thing you want to depend on when it comes to the safety of your child.
The other reasons car seats have a 10 year recommended expiry date, is that over time the harness, tether and ISOFIX straps can all stretch and weaken again leading to less safety than they were originally designed to provide.
Just some of the reasons The Baby Alley only allow car restraints and capsules with no more than a 10 year life span on their website….trying to make safety our priority.