How long does a cordless ( 2007 takes 3 batteries) keyboard last ?

Hi I have a wireless cordless 2007 3 battery keyboard and despite changing the batteries, the little green light will not flicker.

How long should a key board last ?

I managed to eek extra life out of it by rolling up a small bit of aluminium foil and placing that in and it lasted another 6 m, but not any more. I think it is dead, but wanted to check before I send it for recycling !

Many thanks

SallyfromSW20