Generally speaking, the relay strictly refers to the voltage relay. Voltage relay is generally able to work live for a long time, no problem for at least a few years, most PLC automatic control system is also used in this way.

However, there may be other types of relays, such as a small number of special relays, such as pulse relay, two position relay, etc., which are charged for a short time in working principle, and work abnormally for a long time in principle. The coil design does not consider long-term charging, which may burn the coil. There are also non voltage driven relays, such as current relay and current mode signal relay, which can work at high current for a short time in design, but the time is often very short, less than a few seconds.

In addition, although the common voltage relay can be live for a long time, but in high reliability places, the circuit should be designed as far as possible that the relay is not live for a long time, or even use the relay as little as possible. In the relay protection circuit, once the relay fails, it may cause serious consequences.