Expanded Polystyrene (EPS) foam, the primary impact-absorbing material in the Retrospec Lennon, is known for its durability but is susceptible to degradation over time, particularly from prolonged UV exposure and certain chemicals found in sweat. While specific UV resistance data for this helmet's EPS composite isn't published, typical EPS can lose up to 10-15% of its shock-absorbing capacity after 5-7 years of regular use and exposure to direct sunlight. Sweat, being slightly acidic, can also slightly compromise the foam's integrity. Manufacturers generally recommend replacing helmets every 3-5 years, or immediately after a significant impact, to ensure optimal safety performance, as the foam's cellular structure can become brittle.

The Retrospec Lennon is designed to meet standard cycling helmet safety requirements, which in North America typically means compliance with the CPSC (Consumer Product Safety Commission) standard for bicycle helmets. This certification ensures the helmet can withstand impacts up to a specified force. In Europe, it would likely adhere to EN 1078. However, the product specifications do not indicate the inclusion of advanced rotational impact protection systems like MIPS (Multi-directional Impact Protection System). Helmets with MIPS are engineered to reduce rotational forces transferred to the brain during angled impacts, a feature not evident in the Lennon's described construction, which relies solely on the EPS liner's energy absorption capabilities.