HBD can absolutely break if it gets too popular.

If the demand to hold our debt outstrips the demand to buy Hive then the debt ratio will go to 30% and our haircut mechanic will be activated. Now that I'm talking about it... I'm not sure what would happen in this scenario. I assume that the haircut would not apply to Hive >> HBD conversions (only the other way). The only way to fix this problem is to increase the haircut ratio or reduce the demand for debt (lower interest rates).

The problem with increasing the ratio is that it increases our exposure to risk and unnecessary leverage. If we can be sure that people aren't going to dump HBD during the bear market then increasing the ratio is fine but that tends to be exactly what people do in a bear market.

So May next year for complacency?

It's not really possible to superimpose the timelines onto crypto.
Euphoria could be November 2025 which is a normal peak.
However it's arguable that this isn't euphoria if it's like a 2021 situation where that second peak was only just a little bit higher than the first one. In 2021 we could argue that we didn't even really get that euphoria phase in 2021 because the run itself was so lack-luster (unless you're an NFT bro or DEFI degen). We sort of went from 'belief' right into 'complacency' back then because we believed we'd continue going much higher even though 2021 ended and the 4-year cycle was over.