We didn't do Perdido that time. We did Goriz from Nerin, starting at around 9am in Nerin(after a 2+ hour drive from home). Long, longer than you expect. At first you don't get a feeling of being close to a great massif of mountain, but once on to the Cuello Gordo you realise.
We had good views of Ordesa and Perdido that day (often in mist!) Had a coffee in Goriz and left there at 3pm to retrace our steps. Later we went back to do Perdido, from Nerin, but getting the bus up from the village to the col and walking in from there.