Prism desilvering is not a reliability problem, merely cosmetic one. Leica still has new prisms and some (Dag) can resilver them. You can bet what you like (four out of ten?) but Leicaflex shutters are just fine. Mine SL serves me fine too, it was serviced (just regular maintenance) in 2009 and built in 1968.
I believe you, and I am taking note, but: How's the weather in slovenia?
Here in lima, with tons of humidity, my friend who is a collector and has MANY leicas in general, has no working Leicaflex camera. All of them have shutter problems. He has three or four. Of course, i understand they can be fixed. But conversely all his F2 and F cameras are just fine.
Prism desilvering is a serious problem when you can't focus anymore because it is dimming the center of the viewfinder view.
Otherwise, if my friend had a Leicaflex with a good enough prism and a shutter that works, no matter if the speeds are a little bit slow, I would have bought it from him. On the other hand i bought from him a Canon New F-1 more or less battered, the AE prism smashed in the top, brassed and worn, and dirty. It worked perfectly and still works just fine, including metering, AE functions, and of course all shutter functions. Granted, it is a much newer camera than a Leicaflex. But also, a Nikon F from about 1970, with the shutter curtain wrinkled (!), works just fine save for sluggish speeds. Got it serviced - now it's just fine.
Moreover, I also bought a Nikon F from 1967 which needed absolutely zero service; everything worked perfectly from the start. (Photomic finders are another issue)