How many days do you need in Deir ez-Zor?

Two days, and they are two different jobs. Day one is the city: the museum in the morning, the riverbank and the bridge towers in the afternoon — that fills half a day, and the rest goes on arranging transport. Day two runs south-east to Dura-Europos and Mari; there are only 30 kilometres between those two, but it is about 95 from the city to Dura, so the day starts early. Do not squeeze Halabiye into the same day: it lies to the north-west and is a half-day of its own. Out in the countryside, shade, fuel and water are all your own problem — think about all three before you set off.