Rumtscho dá a resposta nos comentários:
No more than 4 hours spent between 5°C and 60°C, cumulative since purchase (assuming the butcher followed correct procedures). It is very restrictive, but most people think it is sensible to follow it (and American restaurants are legally obliged to)
E sobre o congelamento que vou usar:
if you want to stockpile bones, freeze them. They will keep for months that way. This question was about a refrigerator.