I ran this little tool on ROOT’s git repository. It collects data relative to the time each line committed spends in the project before being overwritten.
[li]stack_plot.png: count of lines committed over time, sectioning by year[/li]
[li] survival_plot.png: percentage of commits with a certain lifespan, over lifespan (in years)[/li][/ul]
I thought it might be interesting, and a comparison with other big repos is possible by looking at their plots here (same link as before).