Oia is on everyone's bucket list to get a photo of the sunset, and it is beautiful. I would say to see it once it Oia then travel to Fira, Imerovigli, and other villages to get different beautiful views. Most people start waiting two hours before the sunset in Oia outside and at different restaurants. It is hard to get reservations during that time. And once the sunset is over with, the mass exodus of people is crazy and unsettling. Go to Oia, book a reservation to experience the view at 8:30pm or so. If you have more days travel around where it is less noisy and still an amazing view. We had such a peaceful sunset view in Fira where there were no people standing or watching the sunset. It was amazing and so different from the sunsets in Oia.