Clean your mail box is a good thing for the planet but it's also boring, let's write a script for move your mail older than 1 year and not starred to the trash in Google app's script
Open with your google count google app's script, your are on the start menu, go to my projects, create a new project and then go to the editor section.
Replace the function "my function{}" with the code in the code.js section
Go to the section Trigger and add new trigger (button bottom-left) with your setting, mine are : once a month on the second day.
You can test the function cleanUpMyMailBox imediately with execute button. After that you can easily change as you want the code to move the mail, for example, older than 2 month. Here, a little recap of search operator in gmail