My feelings heavily replicate the OP
4, 4S, 5, 5S, 6+. Every year was the mandatory upgrade. If I didn't give my 6+ to my daughter, I would still have it. But I like the X. Smaller, no bezels, same screen size, no home button. Ill just keep it a good while I'd say. I dont upgrade my car every year to get that extra bit of chrome on the new model.... Same with phones now
Edit: In fact I only update the OS on it and the iPad Air 1 and iPad Pro 12.9 whenever I get round to it, no rush