I don’t know shit about mobile dev but is that allowed today? E.g. Breez wallet will complain in a notification to you if you don’t open the app within 24 or 48 hours, asking you to open the app to sync to the tip of the chain etc. 

 Background tasks are killed also if you force close the app. That's why we show a notification.  

 I don't force close apps very often but it usually doesn't complain do that might be why