If bicycleridr4life is riding off-road, the headset may, indeed, be working loose. This was a constant problem with mountain bikes back in the day and there was a whole cottage industry built around locking headsets that included shaft collars and locking nuts. Here's a couple of examples.

On the other hand, if the current headset has loosened after only a few hundred miles and has done so several times, the cups and races are probably damaged and the headset needs replacement anyway. I'd probably go for the sealed bearing unit over the needle bearings. The sealed bearings are easier to replace if necessary.