80% will be locked for two years in a smart contract that will buy back BNT for 0.01 ETH (the initial price) whenever it is available, according to its calculated price.
The Community of the Currency
Galia Benartzi

I was reading somewhere else that there is a limit of 120k ETH for this program, and it looks the same on https://www.bancor.network/bnt.

When the floor runs out before the two years is up what happens then? Looks like some has already been eroded away or am I missing something here?