From Madd = Correct - not all runways are such that you are truly operating with ASDR=ASDA. But unless you actually do the calcs - which for a line pilot, or even an airline performance department, involves going OUTSIDE the scope of the approved data - you have no idea what actual margin you have.
Madd - I think you figured it out.
I have never showed up to the airport and picked up the 'package' of canned flight plans, performance calcs done by dispatch, ect....
Maybe when you run the numbers ten thousand times...you start seeing things other guys don't. Actually this process started a journey of asking deeper questions about flight testing, performance planning......
A boss once said I had too much time by myself up there to 'ponder my predicament'
You know if these conversations ever get to 'go' maybe we can talk about the tough trips that had me scratching my head during planning.