Getting Shape Dabs to Fade By Age

I am having a rough time getting shapes with write on to fading correctly with
"particle age" the way that particle emitters do.

Here is my scene.

Create a camera, and a perspective view.

Create any outline shape.
Turn on dynamics, local 3D and facing camera.
In dynamics set age to 5
(also add a write on behaviour the shape)

In color range set the opacity to time 0% opacity 0
time 25% opacity 100
time 75% opacity 100
time 100% opacity 0

Now when the dynamic dabs die, they pop out of existence
and do not fade in and out smoothly like particles would.
Since the help says dynamics converts dabs to particles and gives
them a lifespan, you would think they would honour opacity by age?

Any ideas? Am I missing something?

Unfortunately dynamics applied to paint strokes doesn't give you all the parameters of a particle system. In particular, you can't change the opacity over life, which is what you would do to make the particles fade out.

Thanks, I thought so.
What I think I will do is link a particle emitter to a path, and this will give me all
the benefits of particles and age-fade