I have been keeping hens for donkeys years and keep the eggs in my Aga warmed kitchen Winter and Summer, not in the fridge. I've never had a problem but they are either used, sold or given away with only a few days of laying. Recently I found a hidden nest with 15 eggs in so we used them rather than risk giving off eggs to others. So, I should think that the oldest egg was possibly up to 2 weeks old before it was found and I kept and used them over a further two week period. Each time I used one I cracked it into a bowl first just incase. They were all perfect. Hope this puts your mind at ease.
OL