That gives me roughly 10% improvement:
# from
100 145.22 sec/1000  ->  7305.26 min total
200 140.84 sec/1000  ->  7084.80 min total
300 139.62 sec/1000  ->  7023.46 min total
....

# to
100 129.39 sec/1000  ->  6508.96 min total
200 129.43 sec/1000  ->  6510.97 min total
300 130.56 sec/1000  ->  6567.64 min total
....