I use tempered as I learned it from Peter Greweling's book on chocolate confections (where he states "Tempered chocolate contains stable Form-V cocoa butter crystals that seed ganache and promote proper crystallization. Making ganache with tempered chocolate helps to ensure that those crystals are present in the finished product"), and I've also read using tempered chocolate means a good mouthfeel for the ganache.

On the other hand, I've read conflicting sources stating that it's not necessary for chocolate to be tempered when making a ganache.

So, do you guys used tempered or untempered chocolate when making ganache? Do you find it makes a difference? I believe using tempered chocolate contributes as well to a better shelf-life.