I prefer to take my time and always at least take a day to think about it.
I also like to do further research on the street/area and any issues that I might have overlooked (although I always check crime stats and long term flood risks before viewing). I also go back to see the property at different times of the day.
Recently I almost made offers on a couple of properties but further research revealed that one was next to an Airbnb and I also realised there was a small stream quite close to one house at the back, nothing showed on the flood risk map but further research showed that it was there.
With another, the tenant was there on the second viewing and told me that the kids next door could be quite noisy and one of them played the electric guitar. Same thing with another property: the tenants was there and told me that the lady next door had a history of having loud parties and the council had to be involved. I also had a further pic in their garden from a different angle and it was full of garbage...
I would never make an offer on anything on the first viewing because of that. I would want to have a second viewing and do my research.
I know that means I could lose the house to someone who is quicker to offer but I would rather that than make an expensive mistake.
Also my budget is not high so a lot of the properties I am viewing need work and often I need to research how much a specific update would cost. For example I started seeing older housers with back boilers and had no idea how much that would cost to update/remove.
I guess it is different if you already know and area very well and are viewing houses that are well maintained/already upgraded and the process would be quicker.