If you put the sontius delay in an fx chain you could put the mixL and mixR controls on one rotary and automate that

Sanderxpander
Doesn't it annoy you to have to create (and adjust) two identical curves for what is essentially one effect? Or did you find any way around this?

I just Link the Mix controls, and shut them down in real time.
 
If you don't want to do this in real time, in addition to Chuck's tip you can use the Tempo Delay if you want to adjust only one curve. But a lot of times I want the MixL and MixR curves to be different, so the Sonitus is good for that.

Sorry for not getting back earlier - thanks for the tips. I guess a really basic fx chain with L/R mix on one control makes most sense. No idea why I didn't think of that earlier. Almost as easy as inserting H-Delay :)

Thanks everyone.  There are plenty of tips here for handling "ending-delay" repeats...good stuff!