Clicking the "Keep me signed in longer" checkbox will keep you signed in to your GreenCast account on this device for a longer period of time, so you'll be asked to sign in less frequently. To make sure that your account remains safe, you will still be asked to login with your password if you do not visit this site for 45 days.
To prevent others from accessing your GreenCast account, we strongly recommend that you don't check this box on devices and computers that are shared with other people.