Oh, yes, my boxes always get searched, too. To the point where I have learned to instruct the ticket agent to put the luggage tags on so that they do not fall across the seam of the box, which will be cut open. I have wine carriers I have used a dozen times and the TSA re-sealing tape weighs more than the cardboard at this point.

I think that the vast majority of checked luggage I have done is liquids like wine, alcohol, beer, etc. At one point I checked a box with dishes and bubble wrap, but that was not cut open and re-sealed by the TSA

But I generally think anything liquid, dense, or electronics in a box is almost guaranteed to get opened and searched. I think TSA takes anything 'irreversibly' sealed/locked as a challenge.

If you do purchase items on your trips regularly, you could invest in a compact duffel that is checked-luggage sturdy, but will fold up small inside your outbound bag. In the long run, it would probably be cheaper than buying new boxes every time.
http://www.amazon.com/Samsonite-Tote.../dp/B004YZCZL4