The Nokia MixRadio app has seen a minor update to v18.104.22.1688 today.
The update now offers automatic refresh of offline mixes. Offline mixes will try to refresh after 20 days when the app is open and connected to Wi-Fi.
Users can now also search for mixes, and mixes will now be recommended to you based on your music profile.
The update also features the usual bug fixes and performance improvements.
Download it here from Windows Phone Store.
Thanks Danish for the tip.