Actually, I think she was really busy with ice shows at the start of the off-season...? I don't speak Russian, but I think that is what this article here mentions at the beginning (according to GoogleTranslate)...
http://www.sports.ru/others/figure-skating/1021723578.html
If I had to *guess*, I think part of the reason Lena has so much energy is because she really, really loves to perform in front of a live audience. I found this old interview from right after the 2013 Junior World Championships (scroll almost all the way to the bottom--3rd to last post), and I thought Lena's last reply was really revealing of her personality:
http://figureskating.ipb.su/index.php?showtopic=918&st=200
I think Lena might care a little bit more about winning now, but I think that entertaining the audience is still very important for her, and that's why she puts so much energy into everything. And I think that's why she fights so hard to do a perfect performance, and doesn't give up even if she makes a mistake--it's because she wants to put on a good show! :agree:
Hopefully she can maintain that energy! Radiant Radionova!!
But she is only 15 (almost 16). I know that Mao Asada, for example, felt that it was so easy to jump, jump, jump when she was younger, but then when she got older, she would tire more easily. So I guess we will see...