Shimano here too- starts out all shimano, then gets cheap stainless inners when I need one, which isn’t often.
Have to admit I don’t really know how long it lasts, I’m a serial bike and component swapper so it’s pretty rare that it gets left undisturbed for long enough to wear out. But then I reuse stuff whenever I can so I just lose track of it all. I know I just had to replace an inner and a chunk of outer on my commuter but that’s after at least 2 scottish winters, maybe 3, and the shifter had worn out too. Once you get to that point there’s no point really thinking about it imo…
I’ve sometimes wondered about lighter options though as I’m a weenie, I think that’s the only thing that’ll possibly convert me.