I find that when I make a whack of risotto, as I do do because I'm too lazy to stand over the
element again the next day, I use about the same amount of time. But that will vary depending on how well cooked you like your rice.
I would also think that 1.5 cups of rice will take about 20-25 minutes, but 3 cups will probably be no more than 30 minutes. Just use a pan that has a larger surface area over the heat but will still give you enough depth to keep stirring as you will have LOTSA rice in there.
I love risotto, make it often and am now less likely to complain about the time. There are just so many ways to make it wonderful.
Good luck.
BTW...instead of doubling the oil, you could use 2 T. butter, 2 oil. Might be tastier.