Other scenarios can influence the use of "when level fly speed..."such as 2 a/c descending on speeds to be level by a particular point. This could be a standing agreement between two sectors or co-ordination with next sector or centre. Many a time i have had a call to reduce speeds ...ie 250kts by next sector mid way through the descents. The descent profile and current speed they are operating on means an adjustment in speed would end up with them not making their level. Being level in todays enviroment is crucial in most cases.
So.. "when level fly speed..." is a logical answer to this as they make the level and the speed for the next controller.... although........I have never had to use min speed :-)

055166k hope slam treating you well...place not same without you

45 before POL - what happens if the next sector give continuous descent so they do not actually "level", you didn't say "on passing level". I know it is pedantic, but search other threads on here and you will see that there are those out there that will use that to their own advantage, and I have seen it once in real life. It only takes one numpty.......

That is why I teach "when passing <point>" or "250kts at or below FL***"

5MB, if a pilot checks in with me telling me he/she has been given descent with a reduce when level I will either. A) let him level and reduce speed, B) tell him/her to reduce speed and not worry about the height (when appropriate) C) if I give further descent I will specify when I want the speed reduction. I base my decision on what I need and why the previous sector gave the restriction. It's the same with level by restrictions, as if I give further descent it cancels the previous instruction - if I (or the transferring sector) need the level restriction I will restate it.

I would probably be accused of over controlling at times but as others have said we work to the lowest common denominator and if it ensures a safe orderly and expeditious flow of air traffic in the system then that's what I'll do. As much as possible I try to let the pilots do the flying - after all that's what they do!
Cheers
Northerner

As someone has already posted 99% of aircraft can't descend and slow down at the same time. What I've always taught and used I will issue one of two instructions:

Reduce speed to XXX then descend and maintain XXX.

Desecend and maintain XXX, then reduce speed to XXX.

If I need an aircraft to level off and reduce speed then start descending again I will issue an appropriate instruction.

If I'm handed off an aircraft that is restricted I will re-evaluate their restriction and either stick with it or issue a new instruction once they enter my airspace.