Clarkii, he got the nem on the 15th, so it's already been 6 days. If it's still not attaching, I would worry. Even though an hour and a half is a little short on the acclimating (I did more than two hours with an IV drip for both nem acclimations), I would think that the nem should have shown some signs of attaching at this point.
Although the mouth closing on the third day was a great sign, it's still worrisome that it's not attaching at this point, especially since it was purchased/acquired not attached to anything.
ZC, what are your exact water parameters?
Have you had your water tested at your LFS or are you testing at home? If testing at home, what method of testing are you using?
What kind of water are you using for tank top offs?
What kind of water are you using when you do a water change?
How often do you do water changes, and what percentage of your water do you change when you do them?
You say that you have had numerous BTA's, what happened to them? Were they thriving in your tank, or did they die? If they died, do you know what caused them to die?