If I have a team that is in a low level conference and I'm able to build up a program that can make it to the NT for about 4 or 5 straight seasons but not be strong enough to get to the sweet 16, is it possible to build a prestige up to B- even if the rest of the conference is very weak and conference prestige and RPI are near the bottom of Div 1?

yes

eta: I believe so. I was going to show my Marquette resume from Phelan, which got to B- without even that level success, but Marquette is like a B baseline or something, so probably not a direct example. I still believe the answer is yes.

Look at my Fairfield and UNI teams.

I got to B- with my Radford team so yeah it is possible.

Yeah, I think I got Princeton to a b- after making the 2nd round of the nt

Checkout my LMU team.....just got to B