Swiss camera manufacturer Alpa says to not change the shutter speed after cocking the shutter on Copal 0 and 1 size shutters.
From their newsletter:
Back in analog times everything was a little bit easier. Photographers were photographers and the number of actuations of the shutters low. Now in the digital times the number of actuations has increased dramatically. This might be the reason why some restrictions become more obvious. Copal avoided to mention that it is a bad idea to change the time ring after cocking the shutter [emphasis added]! To be clear: If a photographer constantly changes the times after cocking the shutter (especially times around 1/30 sec) he or she will destroy the shutter sooner or later. One can observe a golden shiny covering of the aperture blades from the abrasion of copper.
In order to avoid expensive repairs, please check for proper handling!