Don't tell them you're interviewing them. Just go to the airport and hang out, and you'll get the true answer to the "good teacher" vs. "I'm only doing this because I have to to get that airline job" variety.
My primary CFI jumped to the airlines just about as soon as he had 1500TT/500 multi. But, he was a great instructor - We even discussed that at one point (I think after I'd already finished my private) and he said that if he could make a career of teaching, he would. It's just very hard to make a decent living as a career CFI.
So, even though he was headed for the airlines, he loved to fly and loved to teach people how to fly. He still stops by the FBO when he's in town just to do some hangar talking. And, he was excellent not only in the teaching aspects, but also in customer service - He once drove to the airport (1/2 hour each way) just to sign me off for my long solo cross country. No instruction, no charge!
After he left for the airlines, I just went and hung out at the airport, in the flight school. My private was done and I'd started on instrument but was in a financially-induced pause in training. By just talking flying, I found that the CFI who'd replaced mine was every bit the arrogant jerk who couldn't stand to fly something with a propeller on it. (Credit the flight school, he was fired after a fairly short period of time.)
My CFII that I finished the instrument with got the best "interview" of all: He used to be a huge airport bum and I used him as my safety pilot once, before he was ever a CFI. I learned a lot on that flight, and I knew he'd make a great instructor. He got his CFI/II/MEI tickets and I made a bunch of money, and I've been getting excellent instruction ever since.
So, you won't get a good answer to the time-builder question by asking the question. Just go to the airport, hang out in the flight school, and listen to the instructors. Be a groupie, IOW.
You'll learn most of what you need to know without asking a single question, and the CFI's won't be in salesman mode.