According to most experts, there are two main things that contribute to how long a set of shocks last: what type they are (gas-charged vs. air) and how much weight it carries over time. Generally speaking, gas-charged shocks can last as many as 50,000 miles before needing replacement while some types of air shocks may need replacing after just 15,000 miles if they carry heavy loads all day every day. The best thing for drivers who want their vehicles to feel like new is to replace shocks at least once every 50,000 miles.