Hey Martin,
I think he is just eyeballing it, but you can also use this trick:
Say you have a Curve:
Remove the Bevel, Convert to Mesh:
Use your LoopTools Addon (ships with Blender, but is not enabled by default) > Space:

that will evenly distribute the Vertices….might slightly change the shape of the Curve, depending on resolution and how unevenly spaced the Vertices were…
and then Convert to Curve, Bevel:
and back to Mesh:
