Ember Computed Property Listener ceases to function after first successful return

I'm having a problem with an Ember computed property: It seems as though once the template gets updated, it stops listening to changes in the dependency property. But I don't understand why that would be the case.

Here's my template:

{{input type="text" value=searchText placeholder="Search for users..."}}
    <br>
    <ul>
      {{#each user in searchResults}}
        <li>{{user.Handle}}</li>
        {{else}}
        <p>No users found.</p>
      {{/each}}
    </ul>

And below is my controller:

    App.AutocompleteController = Ember.Controller.extend({
    searchText: null,
    searchResults: function () {
        var searchText = this.get('searchText');
        var data = { 'searchTerm' : searchText };
        var self = this;
        alert("Calling searchResults");
        if (!searchText) { return; }
        if (searchText.length < 2) { return; }
        $.get('/searchUsers', data).then(function (response) {
                self.set("searchResults", JSON.parse(response));
            }); //end then
    }.property('searchText')
});

The first time searchResults actually makes an AJAX call and returns data, the autocomplete results get populated, but after that, searchResults doesn't get called again until I refresh the client.