35is for nearly 4 years and over 30k miles. Lightly remapped and driven often enough and fast enough. Always allowed to warm up before exceeding 3,000 revs and oil changed approx every 7k miles or so. 2014 model, and I suspect the later N54 ancilliary parts were perhaps better made than the earlier ones.
Water pump replaced for about £1500 at something like 76k miles, but it hadn't failed there was just a shadow error code that has, on other forums, been identified as a precursor to water pump failure so I replaced & upgraded it as a precaution.
Rocker cover gasket replaced for £600, but I think, in hindsight having seen the gasket that came off, that was a case of spilt oil and auto-hypochondria on my part.
And... that's it I think. Oh, I replaced a few coils, but they're what £30 each? And generally you can fit them yourself in a few minutes. Same with spark plugs.
The 4th damper/shock that wasn't replaced under warranty earlier in life was still going strong with no oil misting and no problems. If these do go, surely it's just an excuse to upgrade all 4 corners to B12 for under a grand? Your local dealer are only getting thousands to replace these if it's still under warranty.
No HPFP issues, no turbo issues, no roof issues (apart from that time I got my t-shirt caught in it while closing but I can't blame the car for that). Never broke down or left me stranded. If I'd had a warranty at £600 per year (they definitely aren't £600 any more though), I would have lost money on it.
Add in depreciation of just £6k over those years and mileage and, given the power etc, I'd say that's a fairly good proposition.
I wouldn't like to calculate what I spent on tyres and fuel (or modifications!), but that's a different matter. A 30i isn't going to have drastically lower costs on those two things anyway.
All that said, I wouldn't buy a 35is or 35i if the prospect of a £1k-2k+ bill terrifies you. It's part of the deal on a car of that age with that level of performance. Also worth bearing in mind that BMW maintenance costs are a lot higher than many other brands. That same water pump & belt job on my Yeti was a third of the price.
A friend of a friend had a very sensible, mainstream, cheap to run 2014 Mini Countryman Cooper SD from new and a few years ago, on 55k miles and after 10k services etc, needed a new engine costing £9k outside of warranty. Pick any car, any engine, I'll find you a load of horror stories about it on google.
