ember waiting for user to complete the form

In ember, I have a form which ask the user their username and password for our remote server and then I want to verify the credentials by making an ajax call. Currently, I am using a custom made component which allows me to bind any action on clicking next or submit where I can verify the credentials and throw errors if needed. But once an error will occur, user cant click the next button (the way component is implemented) and hence second time validation is not happening. So, I thought to make a computed property which will look for username and password (and hence make ajax call when entered). But the problem with this approach is: every time something is entered in these boxes, computed property gets triggered which makes an ajax call (i dont want to make so many network calls for no purpose). Is there a way in ember where we can wait for user to finish the input and then invoke any kind of action?