40 flights of stairs?  Wow.  That's a lot.  I suspect you aren't doing that all at once?   I do 20 flights of stairs (up and down) and that pretty much wipes me out.  I do it all at once, but by the end I'm ready to sit down for sure.  Maybe I need to step my game up.  Old knee injuries may be holding me back I guess.

That's great to hear that you're seeing measurable improvements with your health.  I think part of what makes this thread great is that you get to see how everyone is strengthening their bodies as a result of regular exercise while we try and keep our minds off selling at these levels.