Generally speaking, the 150% time accommodation for timed exams and quizzes applies to exams with a short window to complete, typically exams with less than a 24-48 hour window for completion. It would be fair to let your students know that you wrote the exam expecting that it would take students without accommodations four to five hours to complete, and that the class should plan their writing time accordingly over the course of the week to ensure that they meet 7-day deadline to hand in their work.
If a student has accommodations for assignment extensions, they may still require additional time if they experience an exacerbation in the impact of their disability, or if the one-week turnaround time required them to engage with accommodations that took time to implement (such as having a newly-provided text converted to Braille). If a student asks for additional time and you have concerns about the request, contact the student’s assigned Disability Specialist to discuss your concerns.