Possibly I’m misinterpreting you, but I think you might really be working under a misapprehension overall, 
. There is no free tier†, and the $5 waiver is just an informal courtesy—not a promise of eternal freebies.
Personally, I wouldn’t be surprised if it was quietly changed in early 2026 (the second anniversary of the removal of the real free tier), to make it accumulate uncollected amounts.
@khuezy’s advice is best: minimize your operating costs as much as you can—and always be prepared to pay the full amount next month (without prior warning).
†Unless you signed up before 2024.