How can I store my digital photos for ever?

Arunima wonders if one external hard drive will keep cherished pictures safely available for decades, but it’s not that simpleI read your article from June 2016 on What’s the best way to organise and store my digital photos? Is it not sufficient to save my pictures on one external hard drive? Must I save them on two? Also, for how many years will an external hard drive keep the pictures safe?I have an Apple iMac and until now all my pictures were stored in Photos. Yesterday, I transf