Watch for blade wear
Rounded edges, twisting, bending or a key that needs jiggling can indicate wear in the blade, the lock or both.
Notice unreliable buttons
A fresh battery may solve weak remote operation. If it does not, the case, switches or circuit board may need inspection.
Do not wait for intermittent starting
A car that sometimes fails to recognise the key may have a transponder, keyless or vehicle-side fault that deserves diagnosis.
Test and store the spare
Once supplied, test every function and keep the spare somewhere secure—not inside the vehicle or on the same key ring.