Discussions

I am curious how much data people who stream music use in a month.  
5-6 days a week 8 hours a day?  
Plus other data usage in a month.  
Is 15GB enough?  
Or do I need more?

if your device has a lot of local storage i would recommend that you download what you want to listen to regularly to your device (one big playlist) from home on your home internet service and then listen on the go. streaming services will let you choose what kind of quality you stream at on your network connection that will lower how much data you're using.  
I listen to lossless audio on the go all the time and have never gone over 8GB of my 15GB plan. but always keep an eye on your data usage. switching phones for example. i had a setting wrong and i didn't realize that i was downloading all my locally stored media back to my phone on the cellular network and it ran me over my monthly allotment in no time. you gotta watch.

Depends on what you use.  
 
I use Spotify and I "download" my playlist so that way it will work when there is no internet, so I use very little data.  
 
My spouse uses YouTube, and when he was doing some work for a friend, he would stream music using data and most months maxed his 15 GB.

I agree about downloading the music.  
I would far rather spend 9 bucks a month on Spotify to do that than to pay more data on my phone.

Youtube music allows you to download any playlist or song that you want, your spouse should take advantage of that feature.