Flame Totem + Skill Effect Duration Nodes: How do they interact?

I'm playing a dual flame totem build and a tree I'm using as a guide tells me to get 2 groups of increased skill duration nodes. How do they interact with the totem? I googled and look at the wiki. So far I have only found two things: The totem's life time summoned is increased and I saw a few posts saying that the flames it fires stay around longer. Is this true? Do the flames stay longer or is this just a misunderstanding?

If it doesn't effect the totem's DPS I rather invest the points else where.

No, it doesn't affect flame totem dps in any way, just totem duration.

perhaps the duration nodes are there for different reasons, Immortal call for instance

http://pathofexile.gamepedia.com/Duration