Icloud session constantly expires, how do I disable?

Every time I boot up my macbook, Itunes shows me a popup saying that my Icloud music library session has expired, and asks me for a password. I enter my password, and it goes away. But this popup appears EVERY TIME I bring my computer out of sleep mode. (If I close my laptop for two minutes to take a leak and come back, it's the same popup again.) It's extremely annoying.

Sometimes it even seems to expire mid session. I'm doing something and get interrupted when the itunes app starts bouncing because the session thing expired again. This seems to happen because the internet connection in our area is... well not the most reliable, and any time it cuts out and reconnects, even if its for just a few moments, the session will drop. (Leading me to believe that its not that my computer goes into sleep mode, its that when its closed, it isn't talking to the internet.) Ever since, I've just kept the Wifi off or quit itunes.

I've tried going into settings and disabling Icloud but this did not seem to change anything. Worst of all, I don't even know what Icloud really does. It says something about backing up my music and stuff, but if everything you've purchased is saved on the app store and can be re-downloaded for free, what's the point of it?