83 370 205 hive needs to be converted which equals to roughly 20 258 000 USD
It's not valid for the different prices of HIVE!
Imagine HIVE at $1, and we already have seen an all-time high 1$ in the non-bull market.
If we keep the HIVE as it is for longer time, the chance of converting it to more HBD increases. (assuming price in the moon)
So I would say it's not bad to look for +10 years.
Well if we see a clear surge we could update the percentage, we can do that at every hard fork if we feel like it, or set it as a witness param.
I don't support the idea of putting something important in the witness params as it opens the window for a quick change. But I think we can change the percentage on the next hard forks.