Mileage to Nashville is the least useful number in this whole conversation. What actually decides your morning is which corridor you feed into and how long it takes you to reach it.
US-31 carries you north and south through the city. Saturn Parkway (SR-396) carries you east toward I-65. The local roads between your neighborhood and those two are where most of the variation lives — and where most of the surprises happen.
Someone commuting to Cool Springs is solving a different problem than someone driving to downtown Nashville. Someone working in Spring Hill, or south toward Columbia, is solving a different problem again, and may not care about I-65 at all.
In Spring Hill, five miles in the right direction can matter more than five extra miles on the listing map.
Test the drive you’d actually make, at the time you’d actually make it. That number is the only one worth trusting.
I won’t quote you a fixed drive time. Growth, construction and the hour of day change it constantly. What I will do is tell you which part of Spring Hill makes your specific week easier.