Tardiva is a naturaly upright cultivar. Therefore if you stop pruning it for several years you'll see a 10' tall vase-shape tree with a short trunk. If this would be a look you are trying to achieve then stop pruning it for a couple of years and then come back to it later. The only drawback in such approach would be that after a few years of uncontrolled growth you might have to deal with what is already there instead of training it into shape every year and remove unwanted growth as it goes.
My prefered method of pruning paniculata-tree is to leave just 1-2-3 sets of buds on a previous year growth. Then it will grow more or less simmetricaly and dense.

Thanks ego45. Your tree looks a lot like mine. I would not mind ten feet tall, but if it is all top with the same short trunk it would not be as attractive. So as soon as my newly thawed ground dries out a bit I will prune it.

Do you think the trunk will get taller or would that require removing branches entirely?

The trunk won't get taller. Woody plants grow from the top UP.

I also prune my tardiva just to make it more dense - this is especially important at the beginning, so the shrub do not get naked on the bottom.

Here is a link that might be useful: Ewa in the Garden