Adding my 2 cents.
When you read the various problem posts on this site, and other similar sites, it makes it seem as if anyone who owns an E9X will have a myriad of issues every day of the year costing them $$$$ of dollars in repairs which is not the case. Yeah. German cars are not as reliable as they once were decades ago, but very car is different and depends on many things (i.e. driving conditions/environment, location, terrain, driver habits/style of driving, how they or who maintains it, etc., etc., etc..) so some have very little problems and some have more problems than others. But, not every single E9X owner is a member of this site so you don’t hear from those people. Therefore, you cannot get a 100% accurate representation of those with or without reliability issues. So as long as you stay on top of things and keep it maintained properly, by you or a BMW mechanic who knows how to properly maintain a 335, then it will be reliable for however long you plan to own it.
I bought my 2010 E92 335i new (build date 10/2009) and probably one of the few original owners on this site. It’s reaching its 10th year of ownership since I first purchased it off the dealer lot on 12/31/2009. It still runs great like a well-oiled machine. My ride has 112,000+ miles now and I haven’t had any major reliability or catastrophic issues that has made feel like I need to get rid of it and nor have I had any doubts it’s going to break down on a road trip in the middle of Siberia.
Not too long ago (November 2018) I posted a 100,000 write up. See the following link if you want to read more.
https://www.e90post.com/forums/showthread.php?t=1554599
Yes. I have fixed or replaced various things in those 9+ years, but not all of them happened at the same time and within a very short period of time as you will see in my 100,000 mile post. I have a trusted BMW mechanic I can afford to keep it well maintained and so when I need to get some service done, or sense something needs to be checked, he takes the time inspect the problem and do things right if a repair or service is needed.
As of now, the most recent repair I had done was the water pump (@ 104,000+ miles), which I knew was coming at some point this year. It just so happened back in March 2019 which my trusted mechanic took care of. Other than that, I don’t expect any other issues to deal with besides regular scheduled maintenance which, according to my iDrive vehicle info, my brake fluid is due for a change, so I will be bringing in for service very soon. And, of course, there’s the annual oil change which will be done sometime before the end of this year. Yep! I have been doing the annual oil change for the past 9 years without any issues whatsoever.
Have no regrets of buying my 335 and have no plans to get rid of it anytime soon.
Good luck with whatever you decide.