That's what I figured, we did that with v17 and v18 and we had a few issues. But at the time we were using HP machines that were always having hardware issues. Our new Dells are very stable, I just wanted to see if anyone else had tried it.
I had V18, NX, and NX2 running on the same Dell Precision 530 workstation for several months without any problem. I have different customers at different levels so I was not concerned about compatibility between versions.