I run the app with my Surface Pro 4 and starting with a full charge, can usually get about 2/3 - 3/4 of the way through a scenario before I get a warning that the battery is almost dead. I'm not sure if this is a Surface/Windows issue or not so I wanted to see if it fares better on Google tablets or iPads.

While I haven't really checked, my iPad Air2 holds out very well. By the end of a 2-3 hour session, I have never seen it dip below 50% (this is not necessarily starting from 100%). Basically it is good enough that I don't consider it a factor when I play.

Keep in mind that the surface is a full desktop OS. You may have other programs limiting your battery performance.

On my iPad 2, a game takes me from 100% to 80% or so.

I use an iPad Mini 2, during a typical game of 2-3 hours the battery charge will drop by about 20%. But I know from experience that battery performance changes dramatically with display brightness and quality of wireless connections.

On my Lenovo 910 it varies on how high I have the brightness up. I should also add the caveat that I am always streaming a Spotify Playlist of ambient music but 3 to 4 hours on max Brightness and 4k resolution will leave me down about 65-80% lowering the Brightness to half lowers it by 40 to 50 used. Next time I'll try downloading the Spotify list instead of streaming and scale down to 1080p

iPad Mini 4, we played through Rising Tides for about four hours, battery was around 80% when we were done. We were using a Bluetooth speaker at the time, too. Full brightness.