I'll try to find the reference, but I'm pretty sure that you can get as many NOBC's as you want, but only the eight most recent will "show up" for anyone other than you (basically, any/all boards, I imagine). Having seen some of your previous posts, I'd recommend you get into JOAPPLY and look at some of the units/billets you might want in the future, then see what NOBCs are required/expected of them. If you go SELRES and your unit doesn't particularly care, you might be able to say "I want to be a NGLO, do you mind if I go the school for my AT"; then you're a leg up when applying to that job.
I think most billets show "PNOBC", which is the NOBC you're expected to get relatively quickly, but within 3 years...which is the term of your billet!