Given the fact that logging/reloggin has become a bit tiresome with all the alts, I like to craft between 5 and 10 items at least, depending on the chance ( 0.2 or 0.1) and depending on the prefix I'm after. For example, if I just got the Redoubt version, I'll make 10 of those to get the Veracity one. If I'm being unlucky and I got all the other prefixes first, I'll make 5.
Ideally, you'd RE 1 by 1 to save mats, but the sense of grind would be too strong and an actual waste of time. I just try to be practical and I don't calculate odds.
Yeah, I decided to do this after I recently got frustrated and just directed my guys to make 15 prototype (blue) items. Then I got the artifact (purple) I wanted on like the second one.
That can still happen knowing this, and I'm not sure how useful it is, but it is nice to know.