Changing ascendancy

I know that you have to do the level of trial that you have already completed to be able to change,(unlike the poe 1 model) I am just wondering, if say Ive only done the first trial picked my current ascendancy but then I have managed to either do the fourth or got a runner for it, so I will get all the ascendancy points, could I respec at that point? Or would I have to redo the first trial to respec and then get the rest of the points?