At the bike shop/bar
Velo Cult Bike Shop, Portland, OR | Velocult
And getting various opinions.
51 y/o guy: "4 to 1. 1 month layoff takes 4 month to get back". [tears welling up in my eyes]
30 y/o bartender: "2 week layoff and the cardio, heart rate, everything starts going. But you can get it back pretty fast." [tip that man well]