This is a very critical issue and 100% of the mobile users suffer from this. A mobile application simply cannot keep using more and more disk space, especially when we are talking about a popular application like this.
Are there any Spotify representatives following this community? If there is some other channel to bring development ideas / bug reports in, please let me know. I would not like to repeat myself but there's still an unanswered question above.
To be honest, if this issue is not handled or even responded I think I'll have to vote with my feet and stop paying for Premium after almost ten years.