Fuse life, fuse designers call it: fuse shelf life. This means the fuse is designed to last for how many years on the shelf for sale in natural surroundings (Temperature between -20~40^oC), humidity less than 60%).

Fuse, although there are many fuse types, The fuse life is similar for a unique brand.

For example, Bussmann fuse, the fuse shelf life is around 15 years without opening the original box. Of course, if you don't open the fuse box for 15 years, you still can use it since it's never been used.

Fuse, as we can see, the structure is fixed: Copper Knife (Fuse blade)，Fuse link (Silver or Silver with Copper), Fuse Tube/cartridge. Their physical characteristics are kind of stable.

Fuse life is according to the fuse which is never used; If you have assembled the electrical fuse, the fuse life is not existing, because fuse is a 1-time-used electrical part as it needs to melt when there is overcurrent to protect the other expensive parts such as semiconductors, diodes.

How about the fuse life when fuse is using/in operation?

It depends. If the operating system is good designed, which means the system current and voltage is stable, the fuse can last as long as it's been used, Bussmann electrical fuses are with the history which has been used for 95 years.

But if the system current is not stable, such as Motor circuit, when it starts, there should be more than 10 times of rated current comes. In this time, what the motor protection fuse only could do is, she died, then to protect the motor.