Yesterday, I was able to purchase a Kurt Kinetic bike trainer from a lady in Houston.

The trainer came a quick release axle that she said I was supposed to put on the rear wheel when I use the trainer.

Is there any reason why I can't use that quick release axle 100% of the time instead of having to switch them out depending if I'm on the trainer or outside on the road?

No. For the vast majority of trainers, the skewer (axle) is identical except for the head which is designed to fit in the trainer. As long as it fits your rear wheel properly, there should no problem.

ok. that's what I thought.

Didn't appear to be very different, except that the ends of the quick release were rounded, and both sides were made of metal.

Thanks.

I agree that it's fine to use the trainer skewer all the time, however I have noticed that these tend to be fairly low quality and the lock mechanism eventually gets a little wobbly. No problem on the trainer as the receiving part to the trainer keeps everything in place. After 10-15 miles of chip seal road and the thing shakes loose it's a bad deal. If you plan to do this, always check to make sure it's tight and replace it when it gets sloppy.