The "Two Broke Girls" money counter slowly going up is how I picture my progress toward a free day rental for Avis....

In best case (50% bonus):

1800 points for BOS is $1200 of rental, assuming $40/day = 30 days = 8 weeks (4 days a week for typical Mon-Fri business traveller)

2400 points for SEA is $1600 of rental, assuming $40/day = 40 days = 10 weeks

Say one travels 48-50 weeks a year, that is 5-6 free days of free rental earned.

Of course, the math is very uncertain as the pricing is dynamic. I wonder if they have a fixed rate for each day at each location. Or, it is based on the AWD rate you enter.