And the number of bikes built with Spirit tubes you've ridden is....?

I agree with you on the lifespan issue though. I build bikes with longevity/durability in mind and never use anything thinner than 7/4/7 and that's been for women and little guys.
I have, however, ridden/helped fab 5 different Spirit tubed bikes and they were great! Plenty stiff too.

BTW- 180 average for women? Dude, you need to move to a different town!