It asks on every login or you can opt to not require the second factor for 30 days on that machine via a checkbox when entering the other factor. You can also p

It asks on every login or you can opt to not require the second factor for 30 days on that machine via a checkbox when entering the other factor. You can also print out a list of 10 one-time use codes to log into your account if you don't have your phone handy.