They usually err on the side of caution, so many will give longer recommendations. Some vets will say that with Baytril (enrofloxacin) you can NEVER eat the eggs again. I think most people follow a 2 to 4 week withdrawl with most medications, many do not have vets recommendations available. I would do what you feel comfortable and safe with. There is no point in making yourself worry. If 8 weeks is comfortable for you, then follow your vets recommendation.
Sulfamide antibiotics are not approved for poultry in any country in the world due to growing antibiotic resistance, so there are not many studies being done on egg withdrawal times for chickens. This is an older study that says that 10 days after stopping the sulfa drug should be long enough. https://www.ncbi.nlm.nih.gov/pubmed/1476095