Old guys seem to be some of the most competitive cyclist but some of the worst losers. If I come up behind some cyclist on my fat e bike whom obviously puts in a burst of speed to stay ahead of me I will let them win and at the same time, help them get their exercise. I will back off enough to stay behind them at least 75 yards (m) and as much as 400 yards (m). When they hit a slight downhill they get ahead, when we hit an uphill I close to gap with a really fast cadence. If they get out of sight on a curve, I close the gap. Longest I have done that was about 30 miles. Some old guys on analog bikes are down right animals. The pace some of them can push for a long distance is down right impressive.
If they look like they are really getting haggard I will end their problem by passing with a cheerful note. I am out to help them get their exercise, not harm them.