Does the minimum interest floor save me when everybody bids down to 0.25%?

You can't get the timing distribution from the sale files, and the counties that publish redemption dates publish them per certificate after the fact, so the workable version is to pull two or three prior years of redeemed certificate records from the same collector and build your own histogram by parcel type. Owner-occupied single family with a mortgage redeems fast, because the servicer advances the taxes to protect its position. Vacant land held by an estate or an out-of-state LLC is where the two-year holds live. That split will move your model more than anything else you do.

On the 5% floor, Florida's statute has read that way, and statutes get amended, so confirm the current text and the collector's own procedures in writing before you commit capital. The floor is what makes a 0.25% bid rational, and it also means your return is a fixed dollar amount whose annualized value is entirely a function of a date you don't control. Your whole model rests on the redemption timing assumption. Everything else is rounding.

Florida doesn't make you pay subsequent taxes on your certificate, new certificates get sold each year on the same parcel, which is a real advantage over states where subs eat your reserve. The consequence people miss is that a later-year certificate holder can apply for a tax deed on their own timetable, which forces your certificate to be paid off, usually at that minimum. So your worst holding period is partly capped by strangers, and your best case gets clipped the same way.

At $800 average you should also price the administrative load per certificate. Sixty positions across a couple of collectors is real bookkeeping for a return measured in tens of dollars per position.