They are rightfully advertising it as '5 hours for each ear'. Which, in my case, is actually 10 hours. I only listen to podcasts - and listen to them in one ear. So when one dies, I'll switch to the other while charging the first one. It's really ideal for my use.
They mentioned in the keynote that you can use just one earpod (eg for a call) and it will route full stereo audio through only that earpod automatically.