Measuring the space between frames - a new ruler / tool?

This should be a basic thing but its not really.

When I make an animation I often need to repeat the same distance between different keyframes.

I haven't found any smart way of doing this other than making a new solid on top and using that layer as a ruler - cause i can adjust it easy.

I wonder if there is a smarter way of doing this? Or if a new tool / Smart snapping or other could be made.

I know i can copy keyframes, but in this case i cant use that since its moving a long element to another point (long slide with images). Also there is multible elements i want to messure. Fade in, scroll and fade out.

Here is my simple ruler layer.