[joegr]

There's no reason at all to do that unless there is a leak or another problem that requires the system to be opened.
Refrigerant does not wear out or get consumed. The less the system is messed with the better.

 

[joegr]

...Does anyone know if this is still a good idea? This was from something I was told years ago (probably around 1970) so I don't know it applies any longer.

I think that it is still valid. The refrigerant carries some compressor oil with it, and it's probably good to keep the o-rings (seals) a little wet with it. I'm sure that some periodic movement is good for the compressor shaft seal too.