There is no evidence supporting stretching as a way of retaining your range of motion. There is lots of evidence that stretching leads to increased rates of injury. Many teams and individuals in pro sport have stopped stretching altogether. My old teams have. I know, it's counter-intuitive, and it's not what I did through my career, but stretching, particularly before exercise, appears to be one of those things that everyone thinks works but in fact doesn't.
What you are describing isn't stretching, but resistance exercise.