How does it ride???
You are probably used to them performing like they do. Because they go bad ever so slowly. Usually, you will only know how bad they are until you ride on new shocks...
Quality Shocks last about 50,000 miles... If you have cheaper shocks probably 25,000 miles...
If you have big, HEAVY wheels, it will wear your shocks faster, as the shock has to control more load, (weight) at every bump...
If you can afford it, get better shocks you can get... Decent suspension helps, traction, tire wear, braking, comfort, etc, etc...