haughtney, the point is we give the 10 minutes (or whatever it is) as a starting point and we go from there. You let us know what you can achieve and we then vector or hold accordingly. We're not expecting you to achieve the impossible - it's letting you know the required delay.
slice, where have you been? We've had this discussion every few months for years. Pilots seem to think that because they can fly to cross the threshold to within 15 seconds (or whatever) that everything that influences a sequence is equally precise. It isn't. Closer in departures intrude, wind changes intrude, medevac traffic intrudes, less than perfect pilots intrude, go-arounds intrude, aircraft requiring a different runway intrude, aircraft being able to accept a different runway intrudes.
If we give you a 10 minute delay 1,000 miles out what is that based on? Certainly not reality. 23 aircraft haven't departed yet. Can you pick up 5 minutes in 200 miles because a couple of aircraft are accepting an alternate runway due to a few knots less crosswind than forecast?