0.10 to 0.25 should be ok without being too noticeable.
And I say that only since mobiles are kind of wonky as far as how well they keep track of time.
Something else you might consider.
Containers work by creating all objects associated, and are automatically picked on creation.
You can, in theory, just set any unwanted objects to invisible/ 0 opacity.
So basically, if sprite2 is in a container with sprite1, then sprite2 will be created at the same time, and can be referenced in the same event.