Tumblr v3 Follow Mode Update - Surf Your Followers
Now you have the option of checking out your followers’ new posts. The command is available in the User Script Commands as shown above. When selected, it makes a single pass through your followers in the same manner as the usual check on your followed. It stores its information in the same manner as the original functionality, so there’s no duplication in the case where you’re following someone that in turn follows you.
For those of you that want to check your followers as often as the ones you’re following, edit the script and set the variable scanFollowers to ‘true’.