Leica's average service turnaround is pathetic. You spend a huge premium for the product and are forced to endure a 1-2 months wait on lens repairs at Leica NJ. I guess sending it to Germany is even worse.
I have visited Leica NJ in person twice in the last year or so for on the spot service of my M240. In this respect, they were very accommodating by offering same day service by prior arrangement. Once for sensor cleaning (a very stubborn spot I couldn't remove after repeated attempts) and once for RF calibration. Both times I discussed the generally poor service turnaround times with the CSR, who was extremely apologetic and was very much aware that it was a problem for Leica's customers... Supposedly they're working on it, but who knows!
I've been a longtime Canon CPS member and use their DSLRs in combination with my Leica kit for much of what I do. With Canon I get 3-4 day turnaround and an immediate loaner if I need it... That might be asking too much of Leica, but should at least be a model for them to follow. If service will take a long time, then provide loaners. If I have a loaner, then I don't really care how long the repair takes. It's up to Leica to work faster to get the loaner back in their pool... But as it stands now, I paid for the gear and am the one 'suffering' if it is unavailable while at Leica for servicing.
To tell my own 50 Lux ASPH story: I have the silver version, bought used in 2011 when it was nearly impossible to find any Leica M glass (at reasonable street prices). I received it out of ideal optical calibration - it was rather soft and glowy wide open. Leica Germany fixed it when I was there on a trip, and had them do it with their paid express service, so it only took a week. But they botched the repair - the lens couldn't focus to infinity. I sent it back the next time I was in Germany and it was fixed properly. Except within an hour of receiving the lens, the lens hood and front filter ring, fell off! I discovered that the whole assembly was held in place with what appeared to be a single tiny screw and a few dabs of glue. I don't think this was specifically a result of them doing a poor repair, rather the parts worked loose due to my tendency to handle the lens by the hood, which probably put a lot of stress on that single screw. (A hint to others - handle the lens other than by the hood!) It just added to the feeling that the lens was problematic.
Anyway, I lived with the filter ring taped back on for a couple years until the focusing mechanism had worked itself loose/wobbly, resulting in lost RF calibration and very soft wide open images, again. So gave it to Leica NJ. It took about a month as a 'pro rush' service. Got it back and everything was fine. Except about six months later the focus mechanism was loose again and images were starting to look too glowy for normal wide open performance. So sent it back and Leica NJ replaced the entire focus mount/helicoid (under warranty from the previous repair, which was appreciated). The lens came back feeling much tighter/better for focus action. Except now the infinity hard stop put actual focus beyond infinity. This is not a good thing, especially because I use the lens a lot at the infinity hard stop. Even stopped down by f/8 and I could discern a loss in sharpness in images set to the infinity hard stop as opposed to those carefully focused via the EVF (which was extremely evident at wider apertures). Bottom line was it wasn't right and messed up my shooting style. I complained to Leica and was told to send in the lens and camera, I guess to make sure it wasn't the camera being out. I was able to test the lens on another M body, and it focused past infinity there, too. Normally I wouldn't worry much about sending the camera with the lens. However, I regularly use the camera for paid work and can't be without it for 1-2 months. I have other 50s and can get by without the lens, though would prefer to have it. I explained this to Leica NJ in a number of emails to get a shipping label to send in just the lens, unless they could provide a loaner body in the interim. Silence. For some reason, I have received no replies from them on subsequent messages. Yes, i should phone them... Prior to this I always received an email reply within 24 hours...
During the previous service for the lens, I asked if they could supply a loaner and was told it might be possible. I was also told it might be possible to service it in a couple weeks. So I sent in the lens and was then told I could *possibly* get a 75 Summarit. Seriously? I have nothing against the Summarit line, and the 75 is an excellent lens. But if I want to use a 50mm, I don't reach for a 75... Oh, and was then also told it would take at least a month, if not more... 🙁
My feeling is the 50 Lux ASPH is not a simple lens to disassemble and then get back into perfect calibration. The floating element system probably adds considerably to the complexity. The amount of focus ring movement required to bring my lens back to correct infinity focus is very, very small. Maybe 1mm, yet when it's focused past infinity, the results are horrible, and as mentioned, you have to stop down to at least f/8 to regain close to equivalent image sharpness compared to correctly focused images...