You are correct, at some point one will be declined. However, that point is most likely well beyond 3-5 apps per year. After ~250 CC accounts over the past 35 years, including ~125 in the past 10 years most of which have been kept open for only ~12.5 months, I personally have not yet encountered that situation to a significant degree and certainly not to the extent that it impedes my earning many SUBs.

OP writes that MS has NOT been done, it’s probably doubtful he/she will start MS now. For someone trying to earn lots of points (and miles), I still submit that SUBs are the way to go and that aggressive SUBs are less risky than aggressive MS. There are MANY reports here of shutdowns due to MS, fewer reports of repetitive CC application declines. A MS shutdown is more virulent and longer lasting that a CC decline. MS shutdown precludes ALL further activity with said bank for at least several years, a CC decline precludes 1 credit card for who knows how long, often just a few months.