Shane O’Neill implements a linear backoff strategy:
Pushups are hard! Even when I’m not trying to rep out as many as I can, they still take a toll on the body. Soon a five-minute break is not enough, and I’m taking longer and longer rests.
Fine, if that’s the way we’re going to do this, then I’m going to go with the flow.
I can confirm that pushups are hard. Also, click through for a link to the backoff script.