Airplay audio between MBA (2013) and Apple TV (2nd gen)?

Anyone have the following issue?

I use Airplay to send audio (Spotify, etc) to my AppleTV. It works great. I then use Mirroring to watch a tv episode or YouTube (audio & video). Later that day, I try to connect via Airplay to listen to Spotify (audio only). All of a sudden Airplay will not connect.

When I pull out my iPhone 5, Spotify connects to my AppleTV flawlessly. Why does the MBA struggle to connect when my iPhone 5 has no issue?

Restarting the AppleTV and MBA rectifies the issue. But, it's frustrating that a restart is required. FYI: I use the new airport extreme as a router. AppleTV is hard-wired to airport extreme, versus using wifi.

Thanks for any feedback! Happy holidays.