300kts+ burns more fuel than 250kts, for the reason that less time is spent at idle thrust. You might not feel that the small fuel saving is worth it but your employer might disagree and it's simply poor practise. Think of the extra fuel consumed on a cumulative basis.
I bang my head against the wall (metaphorically, of course) when I see guys quite correctly flying a variable, CI-generated, econ speed throughout the cruise...yet dogmatically sticking to a fixed (and invariably higher) speed in the descent. It burns extra fuel, may save you two minutes at best and is weirdly inconsistent; just fly econ speed unless ATC says otherwise...