It pays to keep your radios in working order.
Remember this - if you have a system of, say, 10 radios, and just two are in need of repair, then nearly 40% of the radio messages will fail. (that's with only 20% of your radios faulty!) And for each of these failed conversations, two of your users will have a bad radio experience, giving the overall impression of a very poor system. This is why it is important to isolate suspect radios as soon as they are found, ensuring your users have confidence in the system.
For the mathematicians amongst you, the formula is f=(2nx-x2-x)/(n2-n), where n is the total number of radios, x is the number of faulty radios and f is the proportion of radio conversations that fail.