Speed Development vs. Speed Endurance is there a difference

It's difficult to answer your question. I might be missing something, but, I don't see what event you or your athlete competes in?

Agree. I would suggest running 150-400m reps at 400- 1500m pace with short recovery for speed endurance.

Eg. 10x400m in 60 secs with 60 sec recovery.

10x200m in 28 secs with 30 secs recovery

Both at or around RP with short recovery.

I use ratio’s for my younger students I.e. 10x200m in 40 secs with 40 secs recovery.

15secs rec for every 100m.

For a distance runner, how much should you incorporate speed development into your training? Should it be year round? I would love some info on how to incorporate it into a season.

how much wrote:

For a distance runner, how much should you incorporate speed development into your training? Should it be year round? I would love some info on how to incorporate it into a season.

I'd say it should be done year round, but be tailored to the other training. If you're in the middle of summer base building your muscles might be too tight to just go full sprinting even for 30m. That's why people advocate strides of ~150m at ~800m pace, less risk of injury, but not providing the same neuro-coordination stimulation. A good coach will break you down and build you back up as a more complete runner that is doing all of the little things year round, not just at "peak season".