Linear Spline with an Unknown Duration

I'm trying to change a value of a parameter at constant rate, say 0.1 per second.

Normally I'd draw a straight line in the Spline Editor, but this time I'm tyring to create a re-usable solution with an adjustment clip whose duration is unknown.

How do you create a spline in such a situation?

There's a LOT I still don't know about Resolve, but generally speaking, isn't Rate determined by Duration?