The best time to repot any conifer is in late fall, or winter. You haven't said if your buds are green yet or not, but having needles 'harden off' is not a criteria for conifers. If you're not planning on cutting any roots to speak of, and the job will equate to slip potting rather than radical change, then I suppose you could go ahead, but if you can lift it all out of its present pot to see how rootbound it is, and if you think it can wait til Nov., then do that to be safest.

I am a commercial grower of Larch, and each spring, when buds are breaking, we bump our larch up to the next largest container. Fron #1s to #2's and so forth. It never seems to hurt them. Spring is a great time to transplant to a bigger container. Now, if you are talking about root-punning or something else, I would wait until fall to do that.
Steven

What species of Larch are you dealing with? European Larch, Japanese Larch, or Eastern Larch?