I too have had over 30 miles from the frame battery, but I also once got only 10 miles! Of course it depends upon how steep the hills are and how fast you want to go up them. Anything above the cut off speed doesn't use battery, nor does coasting or descending (mostly).
I bought the Focus Jam2 because it was the first emtb that I had ridden that felt natural to me, I just forgot it was an emtb. At the time I bought it I was only managing about 10 miles every 2-3 days on my ordinary mtb (knee problems), so the 378Whr battery was not a concern. But as I got into it and my riding distance steadily increased, I started to feel range anxiety. Where I ride the most, and how I ride, I'm good for 18 miles on one charge without having to worry about getting into the red. If I'm planning anything above that or going somewhere new, I take the TEC pack with me. I really do not notice it when riding, or feel it. Although it does not look good, I must admit.
But when I add the TEC pack, I have a bike that is several kg lighter than many bikes that have a smaller battery.
)
