Just a reminder: Even legitimate batteries can leak and ruin equipment. Don't leave any batteries sitting in unused devices. Look for concealed batteries when replacing to make sure you replace them all. Mixing new batteries with old or dissimilar batteries further increase the risk of damaging leakage developing.
I recently bought a pack of four AA batteries from a stall on my local market. I checked there use by date Nov 2009, I thought ,thats fine until I bought another pack from a high street reailer to find theyre dated Aug 2014. No wonder the first pack didnt last too long