Well this time round it suddenly happened one day on the way to work, on my 20 mile commute. Something clicked.
It was cold, raining, traffic was at a constant 40MPH, and I just realised that 75% of the time I am driving in that same situation, or if not, somewhere nearer the speed limit. My CTR is brilliant fun, and there's a single short tunnel I like to blast through with the windows down on my way to work when I'm not stuck behind a eurobox, but for the most part it's totally wasted. I'm changing to a 530i Sport auto for something a bit comfier, quieter and less crashy.
If I still had a 1 mile commute/could walk to work, I doubt I'd bother changing TBH.
I changed from my first car to the CTR because, well, a 60BHP 1.4 Astra is pretty uninspiring.