I have been waiting and waiting. I've waited one week extra until I dared to check if there were any fertile eggs. There weren't. Not even one. And the birds continued to sit on them all this time. The society finches are one of the best parents in the finch world. And somehow they knew if the eggs were "empty". They tossed out a couple. But with very long intervals in between the empty eggs.
Funny enough, after I've removed the eggs the birds acted as if nothing has happened. They took a bath more than three times (they have been avoiding doing it while incubating), ate more food and hopped around more vigorously.
I left the nest inside the cage. In case they decide to give it a second try.