I don't know. I've run more multi days than fixed distance events. I tend to run more 3 days but am gearing up for another 6 day and then Sri for 10. Do I walk some during these? Yep. Is it easy? Not at all. I've had kidneys shut down and have been rushed to the paramedics, I've sustained permanent eye damage during the Tahoe 200. I love it though. Is it easier than a 20 min 5K? For me yes, as I've never had top end speed but I can suffer through almost anything and it's why I once survived for 4 days after an accident in Alaska with no food. Then again, is running a 16 min or 15 min 5K really that hard? I mean wow can't you simply suffer for 15 mins? It's not that long.
I personally think anyone that calls 5 or 10Ks distance running is just full of it. They have no clue but it's not their fault. They probably love all of those participation medals lol. It's ok. The world needs these sissies too (well, I suppose).