If I travel for work every week, do I shorten the prayer for the whole trip?

The traveller shortens the four-rakah prayers so long as he is travelling and has not intended a stay that takes him out of the ruling of travel. A weekly work journey is travel while on the road and in a place he has not settled. If he intends to stay four days or more, according to the well-known view he completes the prayer. He should look at his actual intention in that town, not merely that he often travels.