Pitotheat and others,
What you are describing is a dynamc environment.
The ATC system works around a basic plan.
Yes it does take differing times to dipatch an aircraft.
A plan based on normal assumptions!
We rely on your ESTIMATES. If your estimates suddenly change then that is your problem...slot of 2000...we have late pasengers, unserviceability, blah, blah...
Pilots are extremely good at (trying to) bring other people down...and that is your bane. Your conditions are going the same way as your attitude!
There are too many people wanting to "track direct".
Your ego is your detriment!
"How dare he say that"..."More fool you".