@Proton2: In the big picture, what percentage of people buy smartphones off-contract? I don't know, but I would think it is a pretty low percentage. Hence while those people might be more likely to do an impulse switch, I would think the vast majority of people won't pay ETF to do impulse switches.
And even for people that do buy off-contract, how many of them just randomly switch every few months?
So I believe my observation that installed base lags current phone trends by a significant amount of time is valid.