Here are a few reasons why having a spare key is a good idea:
Obtain a spare car key when you still have a working key will always be cheaper than if all keys are lost. When you already have a key, we carry out less work to program a spare key for your vehicle. We won’t need to picklock and decode the lock on your vehicle to cut the blade.
Having a spare key stored somewhere safe means you won't have to worry about misplacing your keys or locking them inside your vehicle, For instance, you have locked the key in the boot of your vehicle you can simply use the spare key instead of having to wait for a locksmith to arrive to open the car for you.
Easier for Two Drivers
Having only one key to a car when more people are using it increases the chances of the key getting lost. If both of the drivers have their own key to the car there is less chance of the keys getting misplaced and lost.