So my Zeus runs in the background most of the time because I also use it with NWC for sending Zaps myself. So most of the time for me zaps I receive just come right through without any need to manually settle. But I have received a few zaps while offline and they just settled when I opened the app next and saw that I had a zap to receive. Personally I use it because I was previously hosting my own LN address on my own domain, but decided I didn't want to expose my own IP on my own web server any more. So this was a good non-custodial compromise.