Yesterday evening, I ran the PostgreSQL regression tests (make check-world) on master and on each supported back-branch three times on hydra, a community test machine provided by IBM. Here are the median results:
9.1 - 3m49.942s
9.2 - 5m17.278s
9.3 - 6m36.609s
9.4 - 9m48.211s
9.5 - 8m58.544s
master, or 9.6 - 13m16.762s