Hours and Years
Two to three hours is pretty standard for a viva. Sometimes less, sometimes more. Two to three hours is the right neighbourhood.
Three to four years is pretty standard for a PhD. Sometimes less, sometimes more. Three to four years puts us in a meaningful ballpark.
People worry about “long” vivas. Mine was four hours. I’ve heard of the occasional six-hour viva. It can seem like a long time to be on and discuss your research. But you get to those hours of discussion after years of work. You’re in a good place.