If you haven't applied for any other Citi cards in a couple months, you can apply once for a second card 8+ days later. But for your third card, you have to wait 65ish days from the first card. So the "8 days" is not repeatable back to back.

So unless this offer gets extended, it's impossible at this point (less than a month before the offer is scheduled to end) to do a "constant" churn at 60k.

However, for years the offer has been 50k, so you could do a fairly "constant" churn of that (assuming it continues to stay around), at the limit of one about every 33 days (on average). But: If you keep up that high a rate of "constant" churn, you better not be applying for much else (even from other banks), as that by itself will get you very close to Citi's typical "no more than 6 inquiries in the past 6 months" limit (inquiries = hard pulls).