I think the limit may come with falling VIX. This strategy works great in high vol environments like now. But once normality returns to the markets (and I hope it doesn't for a while), then things will change.
As an example, in March, when VIX was 60+, I was successfully trading double cals on the SPX on expiry days just like you are doing the IC's now. Making around 10-15% a day. Then towards the end of April that strategy started losing its shine, and I did a couple of small double cal trades this week, and they were break-even at best.
I guess like in other aspects of life, we just need to successfully adapt to the constantly shifting landscape.