In fact the wisely received wisdom was that Android devices would have longer useful lifespans because open source leads to higher quality software that's maintained and updated for longer, which can be customized by users so it meets their needs better. The reality that many Android devices never see a single software update and are junked up with carrier crapware and poor device drivers hidden in binary blobs still hasn't sunk home for everyone yet.
Even now when I buy a new device I think about how useful it will be and what it's support will be like for 2 to 4 years. Beyond that, there's no way to tell. When my kid's original iPad Minis get replaced, if they still work I'll probably just use them as family photo and video galleries.