I’ve set up two ESP32 boards on different power supplies, one is running my sketch and the other is running a stock standard example sketch from the library file. Both boards lost connection to the server at exactly the same time (04:02am), so it is not the sketch or the board or the power supply. This leaves either the router or the internet connection or the Blynk server.
I also have a Cayenne board running continuously which has not exhibited any disconnection issues, so that appears to rule out the router and the internet connection, leaving the Blynk server.
My concern is that the ESP32 boards are unable to reconnect to the server after a dropout. As you can see from the original post, the board is trying to connect to the server, but never succeeds. It continually attempts, giving this message over and over again
 Heartbeat timeout
 Connecting to blynk-cloud.com:80