The answer is, “When you can’t get the strings anymore”.

It’s a great idea, you can change strings in seconds, just hook the string in at the nut and clip the bottom end on the bridge..

It was a fairly simple conversion,  Change the nut for a locking one…

and install a set of machine heads.  It was fairly obvious where they needed to go but I marked it out to make sure none of the strings foul each other, it is a rather odd shape head….

Drill the holes…

Fit the new heads…

While I was at it I gave it a fret-dress to get it paying nicely.

Once it was all back together check the setup, the tremolo action was a little low and wouldn’t bend up, only down…

so I loosened off the springs a little…

Not quite my cup of tea but at least it has a future now, just doesn’t load as quickly…