A few more tips, and info.
1. If you have a Surface 2, I would recommend you enable "hibernation". This is a feature that Microsoft has had since XP days, created for laptops. The main difference between hibernation and sleep, is that with hibernation, you will totally power off the unit, sleep still has a charge going. In the field, you don't need wifi, bluetooth or anti virus. So I bring up 2 up and disable all of this stuff before I head out, lauch C1 and hibernate the device. Thus when I power on, C1 is there just where I left it and all the other components I don't need are off, and will stay off as long as I select hibernate in the power off options. You will save a considerable amout of battery with this. Also the turning off the wifi helps alot since the connection is no longer actively seeking a connection, which it will do as long as it's on. By default hibernate is not an option on the 2, and you have to enable it under advanced features in power management.
2. As much as I like the Surface pro 3, for a laptop, as Ken first pointed out, it's a bit big around the tripod. You have to be a bit more careful with it when using it tethered in the field. I have gone back to my Surface 2 for now.
3. In outdoor temps of over 95 degrees F, the fan on the Surface 2 will come on. However this doesn't seem to really effect the battery life that much. Extended use in 95 to 100 degree heat seems to task the Surface 2 and will definitely task the Surface 3.
I was testing yesterday with the 2 and IQ260, and after about 20 minutes my IQ260 was almost too hot to touch. Not sure if this is because the Surface 2 was set to charge or not. A back that hot can't be doing that well even at iso 50 in regards to noise.
I have started using the 2 and IQ260 to setup the shot, then go to the card on the IQ260. This does breakup the shoot, but it seems to keep the overall heat down. I have also stopped charging the IQ260 battery when tethered.
4. Sadly, as I thought, the i7 versions are running into overheating issues. These are with both the i7 256 and i7 512. Many users are having issues where the system fan is running a max. Some of the folks are also trying to run high end games on the Surface 3's which I would not try.
My 3 does seem to run the fan during charging, but I have not yet seen the fan run at max any time, but I stayed away from the i7. Microsoft may come up with a design fix in the future.
You can read more about various user issues here:
Surface Pro 3 bugs keep coming as overheating complaints arise | PCWorld
Paul