"Mockingbirds don't do one thing but make music for us to enjoy. They don't do one thing but sing their hearts out for us. That's why it's a sin to kill a mockingbird." - Harper Lee, To Kill a Mockingbird
The goal is to increase the ratio of response and to have good prediction if it can be expected to come or not. If you don't think it will come, don't reinforce not coming by calling anyway. See what I told Ms Onion.