Ok. Now, get your head out of gutter.

Two shower valves (the same model).
Two brass nipples (the same model).

Both turned the same number of times... both connecting the same fitting, etc.

The only variable is the pipe thread sealant (teflon paste). (I may have put too little(?) or too much(?) on one or the other)

One leaks, from both ends of nipple. One doesn't leak at all.

Should I be concerned about the non-leaker leaking down the road?

Thanks for the help,

Pete