Preventive cla is not smart. It will cost you a lot of money and you are not sure what will be done.
Camera repairmen, even the best ones, are not saints. When they receive a camera that needs a 0.001ml drop of oil they certainly won’t go through the whole job of cleaning the whole shutter and relubing. Why would they? Because you asked for it?
Don’t be silly.
They will apply the tiny drop and charge you for a full cla. That’s because they know that you won’t notice. And that’s because the camera doesn’t beed a full cla.
They simply know that the camera will gum up in the next decade, and by then, the camera owner will happily pay. Because it’s a Leica and because the internet people all seem to be ok with a 3-500$ cla, which is total nonsense to me.
And let’s be honest: with today’s ultra sporadic film usage, the camera won’t need a cla for quite a long time. It might gum up, but a workout here and there is enough to keep it going.
You will/should send the camera for a CLA only when 1 seconds becomes longer than 2 seconds, and especially when 1/2 second speed becomes 1 second or longer. 1/60th and up should still act within tolerance at that point.
Before that point, your Leica is perfectly fine.