I mostly vape 6 volts on 901 atomizers. I did get some 510's and an adapter in the mail yesterday and I tried the 510s out today.
They 510 supposedly has a lower resistance than the 901, and will therefore get hotter at the same voltage. I can vape a 901 at 6V fine, but the 510 is way too harsh. It does vape great at 3.7 volts though. I would highly suggest you get some HV atomizers as raqball suggested.
So I would imagine 6 volts on a 510 would be very hard on atomizers. That said, I would think they would last much longer than an hour or less. That combined with the fact the body of the S6 is getting warm leads me to think you just probably aren't keeping them wet enough.
If you are dripping try switching to cartridges for a bit, load the cart up and put a drop or two directly into the atomizer. In my experience, you don't vape until vapor drops with 6V like you do with 3.7 volts. You have to sense the taste change and the increased heat the atomizer is making. It's like second nature for me now, but there is a learning curve and it took me some time. My atomizers are lasting much longer now, a week or more vs a day or two before.
If I vape heavy at 6 volts the outside of the S6 can get warm, I think the aluminum draws the heat off the atomizer. That said, make sure your batteries are not getting hot. This could be a problem if they are.
Hope this helps, just keep the juice in it, worst that will happen is you flood it.