Quite a while ago. Not sure on the exact time, but judging from this article, I'd guess sometime in 2014 https://torrentfreak.com/spotify-starts-shutting-down-its-ma...
If so this is perhaps a dated phenomenon. Moore's Law is still a thing and today's generation of mobile devices are getting fatter and fatter.
Moore's Law eventually will matter, since faster and more efficient chips equal the ability to do more with lower power consumption. Batteries aren't getting better fast enough, but power consumption per fixed unit of compute is falling like a rock. As a result "effective battery life" for a given fixed workload is subject to Moore's Law.