No reputable trainer recommends alternating rounds. It's an old debate that sounds fun on the Internet.
Ding Ding Ding Ding Ding...we have a winner.
Using alternating rounds shows a lack of faith in the caliber. If you do not have faith in the caliber, why carry it at all?
This is only an issue in "marginal" rounds such as .32, .380 and (occasionally) 9x18.
Yes, I do own a .380 (LCP). I carry it a few days each year, and it is loaded with DPX. I should probably just sell it, and avoid the temptation of carrying it those few days. My PM9 is only a bit larger, and I shoot it better. Again, I only carry the PM9 a few days per year...