Angular store variable in service

You could do Both. Keeping this kind of data inside the Service in private variables Can isolate it and you can control read/write to do some sort of validation. This way you are not allowing the modification of the data anywhere else but inside the Service.

What you can do is to add a save function inside the service that saves the desired data inside the storage and a public recall function that gets called on the app.run method.

Your service :

angular.module('myApp.services', [])
  .factory('githubService', function($http) {
    var githubUrl = 'https://api.github.com',
      githubUsername;
    var runUserRequest = function(path) {
      // Return the promise from the $http service
      // that calls the Github API using JSONP
      return $http({
        method: 'JSONP',
        url: githubUrl + '/users/' +
          githubUsername + '/' +
          path + '?callback=JSON_CALLBACK'
      });
    }
    //Saves the data inside localStorage
    var save = function() {
      localStorage.setItem('githubData', guthubUserName);
    }

    // Return the service object with two methods
    // events
    // and setUsername
    return {
      events: function() {
        return runUserRequest('events');
      },
      setUsername: function(username) {
        githubUsername = username;
        save(); // keeps the username always up to date
      },
      recall : function(){
        githubUsername = localStorage.getItem('githubData');
      }  
    };
  });

Your main.js: var app = app.module('yourGitHubApp', ['myApp.services'])

app.run(function(githubService){
 githubService.recall();
})

So each time the applications gets reloaded the data from localStorage would be refreshed.