eyeinthesky re. point two in your first post -
Many, many moons ago I was taught (during line training in my first position with a major international carrier) that one should not call "reaching" until within 300' of the assigned FL/Alt. and should not call "leaving" until at least 300' out the current FL/Alt. I don't know if that was/is written in some tome somewhere, but it nevertheless strikes me as good advice.
With regard to pilots asking for descent and subsequently not initiating said manoeuvre until some time/distance has elapsed - that can be easily explained. Many FMC's give timely warning that top of descent is approaching (typically 14nm/2 min.) and warn the crew accordingly with a message such as "RESET MCP ALT". For a variety of reasons (not least poor training and lack of situational awareness) the crew will immediately request descent, programme the autopilot et al and wait for another minute or two (several nautical miles) for the aircraft to comply automatically.
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[ 08 July 2001: Message edited by: Mister Slot ]