Well, the QC 15 was perfect for me for a number of years, as long as I had AAA batteries. And while every new version after had some kind of trade off to it, the QC series has overall been quite reliable, with removable cords, etc. The Bluetooth version added a lot of complexity, but when it works well, it’s magic. And it works more often than it doesn’t, I just tend to notice the Bluetooth stack bugs more when they occur. Similarly I had to replace a number of QC 15 and 25 cords over the years as they inevitably went bad due to prolonged use and abuse, as it were. The Bose store historically made it very easy to get spare parts and service, though I presume that’s changed somewhat today...