Edit 2: As of March 2021, none of these methods will work as google added a captcha button that randomly pops up after some time.

Edit 1: Apparently the solution is very easy, and doesn't need any JavaScript. Just create a new cell at the bottom having the following line:

while True:pass

now keep the cell in the run sequence so that the infinite loop won't stop and thus keep your session alive.

Old method: Set a javascript interval to click on the connect button every 60 seconds. Open developer-settings (in your web-browser) with Ctrl+Shift+I then click on console tab and type this on the console prompt. (for mac press Option+Command+I)

function ConnectButton(){
  console.log("Connect pushed"); 
  document.querySelector("#top-toolbar > colab-connectbutton").shadowRoot.querySelector("#connect").click() 
}
setInterval(ConnectButton,60000);

Since the id of the connect button is now changed to "colab-connect-button", the following code can be used to keep clicking on the button.

function ClickConnect(){
    console.log("Clicked on connect button"); 
    document.querySelector("colab-connect-button").click()
}
setInterval(ClickConnect,60000)

If still, this doesn't work, then follow the steps below:

1. Right-click on the connect button (on the top-right side of the colab)
2. Click on inspect
3. Get the HTML id of the button and substitute in the following code

function ClickConnect(){
    console.log("Clicked on connect button"); 
    document.querySelector("Put ID here").click() // Change id here
}
setInterval(ClickConnect,60000)

For me the following examples:

• document.querySelector("#connect").click() or
• document.querySelector("colab-toolbar-button#connect").click() or
• document.querySelector("colab-connect-button").click()

were throwing errors.

I had to adapt them to the following:

Version 1:

function ClickConnect(){
  console.log("Connnect Clicked - Start"); 
  document.querySelector("#top-toolbar > colab-connect-button").shadowRoot.querySelector("#connect").click();
  console.log("Connnect Clicked - End"); 
};
setInterval(ClickConnect, 60000)

Version 2: If you would like to be able to stop the function, here is the new code:

var startClickConnect = function startClickConnect(){
    var clickConnect = function clickConnect(){
        console.log("Connnect Clicked - Start");
        document.querySelector("#top-toolbar > colab-connect-button").shadowRoot.querySelector("#connect").click();
        console.log("Connnect Clicked - End"); 
    };

    var intervalId = setInterval(clickConnect, 60000);

    var stopClickConnectHandler = function stopClickConnect() {
        console.log("Connnect Clicked Stopped - Start");
        clearInterval(intervalId);
        console.log("Connnect Clicked Stopped - End");
    };

    return stopClickConnectHandler;
};

var stopClickConnect = startClickConnect();

In order to stop, call:

stopClickConnect();