You can refresh the Display iTunes Cover & Currently Playing Track Widget with a Received Distributed Notifications Trigger for a better battery life:
Add the trigger under "All apps" and use:
for the Notification name.
For Spotify com.spotify.client.PlaybackStateChanged should work.
Then refresh your trigger with a AppleScript Action:
tell application "BetterTouchTool" refresh_widget "9C59B932-E282-4A7F-ADC7-E7A212FBC795" end tell
(change the id with your widget id!)
Now you can disable the refresh in the widget configuration: